The #1 belly pan is a real pain to replace. The belly pain is only a part of the complete #1 cross member.
I just did mine. The frame was on a rotissary and upside down. The belly pan is sandwiched between parts at the spring towers. You have to get all the old pieces out with a grinder the fits between the parts. Then you have to bend the new bellly pan at the middle and shoehorn both ends between the original parts at both spring towers. Once it was nested in, I had to use a come-a-long to line it up with the upper part of #1 cross member.

I would hate to try this upside down.

And don't forget, the lower A arm brackets need to be replaced and placed in the right position as well after the belly pan is put in place.

This is the second worst thing to replace on the frame. The worst is #3. The enitre rear end hangs off that one. I had to build an angle iron frame around the frame just to hold the rear frame in position while switching out #3.

Your transmission bracket and spring towers are in worse shape than mine were. I suspect you have a lot of other rust issues on the frame.

I spent over $2000 on parts and all last winter repairing my frame. Was it worth it--no.
I should have just bought a new frame at $4500. It would have been a lot easier and I would have a lot farther in my restoration.

Steve L
73 coupe since new

 

Good info, Steve. I am in the same position as the OP, and it has really shut down the progress with my 69 while I try to figure out what to do.

At first, I thought just the belly pan was bad, but further inspection showed that the whole crossmember is bad; almost like it sat down in the mud for a long time. Rest of the frame is OK---rails, kickups, mounts are good. Birdcage is reasonably good (at least for me). It shows some rust on the #2's behind the kick panels, but still solid enough. Windshield frame/channels are great--even pulled the glass and dash to get a good look at it.

I'm at a loss to understand what happened to the front crossmember on my car!

I thought I checked the car out well enough when I bought it, looking in the typical areas, but honestly I did not pay good attention to this area; in fact I never gave it a second thought. Thank God the car was cheap!

I was lucky enough to get a front frame chunk from another CF member, and I cut, chiseled, and ground the rest of the side rails off to leave me with a good crossmember. That was quite a job itself, with it laying right in front of me.

My plan is to pull the suspension and hack, cut, and beat the old crossmember out of the frame. The pockets it fits into the side rails should be good for a few new word combinationsI

'll keep up with this thread and let everyone know my progress. Just waiting for it to slow down at work so I can pull the car into the shop to dismantle everything. I will be attempting to do this surgery body on and upside down

 

My gut feeling is that with many of these cars if one section of the frame is shot there is bound to be another area that is also in bad condition. On my frame I had areas that looked ok, but when I took an awl to it I found that most of the frame was shot. When I pulled the body it was even worse. I was lucky in my search for a frame. I was able to get a restored frame for a little over $2000 delivered a couple years ago. The guy from Americas Finest gave me a good price and he has many frames in stock. Good luck.

 

I did inquire with Corvette USA last week for a 'new' frame for my 1976. A coated frame for an automatic came to a price of $ 2.950,-. When looking at some of the prices for driver Vettes, then I think this price is somewhat to the high side.

Hope to find a decent priced frame soon (preferably from California or Arizona).

Edwin