Ok. So, dumb question: what the heck is actually inside the cage nuts that are welded to the frame rails?
I thought it would be a 2 side cage bracket with walls front and rear and openings on each side. That's what is looks like in the AIM and also what I can see on my '69.
However, 2 of mine ended up rounding over and are spinning with the bolt, BUT.... I can't feel anything movung from putting my finger on either side of the cage when turning the bolt. I thought I could wedge something in there to lock the nut up, but I can't actually detect what is spinning in there.
Is there some kind of insert within the nut? Or did I have something break loose within the nut itself?
I bought 2 replacement nuts, and they're just 1" square nuts.
I'm hoping to eventually knock the bad nuts out from the side and replace with the new ones, but of course the bolt seized and rounded the nut with only about 1/2 to go before full body button-down position.
Any help would be appreciated.

 

Sounds like it's that time.....

 

I think I see my error. I've been feeling the wall off the mount bracket "doghouse", not the actual cage or nut. I need the access the open sides of the doghouse so I can wedge something in those little corner openings in the cage to try to hold the nut tight while I back the bolt out.
I don't have access to an acetylene torch, just a little wire welder. So what are my options for repair? Can I put a permanent wedge in between the cage and nut?

 

Unfortunately your options aren't great. The body mount you posted can only be gotten to by removing the body, remove it the old one and weld in a new mount. Or if it's the #2 or #3 location you'd have to cut out part of the bird cage/frame install a new mount and repair re-weld the bird cage and I don't really think you'd want to go there nor would anyone else for that matter I don't think.
I wish I could be of a more positive reply but from my humble experience this is the way I see it.

 

i have heard of people driving a straight punch into the mount cage to hold the big square nut. unfortunately access to do that is severely restricted. most likely workaround is a dremel and cut-off wheels. only thing fits in there to cut off the bolt heads. or a torch and burn off the head, but thin rusty metal around that bolt head could be a victim of that method. nut is already spinning in the cage. so the nut and cage really have to be replaced. you could cut the cage off or open and install the new nuts and weld back up, but it is a lot of fab work.

 

I caveman banged on the side of the outer cage, then cut the lower seam of the flap (top side of the part picture) with a dremel. That revealed to headless bolt remains. I used a skill saw/jigsaw with metal blades to twice cut through the bolt (above and below the square nut). The little bit of the nut that remained within the frame came out with a small magnet through a frame hole. There's still a solid part "roof" on my number 3 mount, that'll allow me to put a couple washers and a nut from the body mount replacement kit I bought inside/under the "roof."

I burned through five metal blades on that one side with that "Bubba" move but got the bolt out without doing too much damage. I took a while and totally sucked... super frustrating. It was the only way I could figure at the time to get a blade on that bolt. (I have the body off the frame only separated by 4x4's for mount access.)

On the other side #3, I've got to try something different. So I PB Blasted the whole thing again and will try an extractor head on the headless bolt after some Memorial Day celebration today. Good luck. Let us know if you discover a better way. I'm SO ready to be done with those dang mounts.

 

OK - So I figured out how to get the brand new stuck #2 bolt out of the spinning mount nut.
I took a break yesterday with my 25 year old son, went to bring my father some Chinese food at his nursing home, and shared a COVID picnic with him, eating the food just outside his window. He was in heaven!
Then my son and I went fishing.
Nothing like Chinese food and fresh air to clear your head for added patience.

I first cut off the bolt head from inside the speaker pocket using an angle grinder with a used cut-off disk: used, because the diameter had been worn down so that it JUST fit horizontally into the opening to get to the bolt head.
Once the head was off, we could lift the body back up again to get a full view of the mount on the frame.
Seems that the 2 "ears" on the cage (front and rear sides) had flared away from the nut, and that's what allowed it to spin.
I was able to drive 2 thick screwdrivers - on on each side of the cage - into the gaps and close those bent tabs enough to retain the nut for removing the remainder of the bolt.
Then, it was about 1/2 hour of continually cranking on a vice grips, turning the bolt from just above the mount, only about 20 degrees per grip.
Finally got the bolt out!!!
Now - the bonehead award of the day gets self-awarded to me!!
Because, in my infinite wisdom, I decided to go with longer new mount bolts, and bought 8 Grade 8 bolts at 3 1/2" length.
My thinking was, that it would give me more ability to get things lined up, and also allow me to keep them loosely attached while I went to the opposite side of the car and lifted that side up to replace those mounts.
Trouble is, the longer bolts still have the same 1 1/4" of threaded length as the stock 2" bolts do. (see 1st photo below)
Sooooo...... my stuck #2 new 3 1/2" bolt was actually due to me driving the bolt so deep that the un-threaded section drove into, and bound in the nut, thereby causing the nut to eventually break free and spin.
Doh, Doh, and Double-Doh!

Now that the bolt is out and I can see what the root cause was, my idea is the wedge some metal pegs (maybe some donor cut pieces of old allen wrenches?) into the gaps on either side of the cage to ensure the nut stays put, then put a tack weld on each to keep them in there for the next eventual removal. (see 2nd photo below)
I think this will still allow the nut to have enough "float" that it will align properly to the body and bolt when lowered.

 

body is still on the frame? 35 bucks each. not really a this-week issue. get it apart and see how many you need. then decide if you really want bubba that deep in the middle of your car or buy a couple of mount cages.

 

Nah - I'm not equipped for HD welding, just tacking and thin metals.
Jamming a couple of "engineered shims" into the cage (a couple sections of cut allen wrenches), and then a quick tack weld on each, and the nut was good and secure, enough to take the torque of the #2 passenger side bolt when buttoning up that side.
Bubba would be proud.
Now, on to the driver's side, and I'm already seeing much more rust flakes from under that #2 mount area - birdcage base is pretty messed up and I accumulated an nice pile of rusty flakes on the floor directly below #2. Interestingly enough, there is no evidence of rust on the inside of #2 - in the speaker pocket - the water must drain from the W/S frame down the outside to get to my crusty area, not into the speaker box.
BTW - I have a suspicion, that the silly foam block that sits on the frame forward of #2 likely contributed more to corrosion than prevented it. Seems that alot of the corrosion is located around the foam block, as if it was mostly retaining moisture and keeping it there, instead of preventing it to get into the #2 mount area.
Any thoughts on that?

 

Here's some photos of my work-around plan for the spinning mount nuts.
Since I was able to remove the cut-off bolts by jamming 2 screwdrivers in the gaps front and rear of the cage nuts (where the flanges had flared open), I figured this would be a good permanent fix.
Since I only just bought a base level wire welder, I wouldn't be able to tackle a complete replacement of the mount bracket and cage nuts.
First picture shows the gaps AFTER I bent them home with the screwdrivers.
Knowing that those cage flanges would likely flare out again under bolt torque, I fabbed up sections of Allen wrenches that would wedge in the gaps and keep the cage closed. (see 2nd and 3rd photos).
I then took my new wire welder and tacked those in place, since I don't ever want to have to do this again!
Not the prettiest of fixes, but given the fact that I had very limited access to the area, and just non-professional equipment, I think this is a respectable repair that doesn't compromise any integrity, and only maybe borders on Bubba territory.