Just a quick comment on using the kit on my '68 roadster, and hopefully provide some clarity to some of the chatter I've read. Normally I would be in the "go buy some bolts at Ace Hardware" camp, but my stock rubber bushings were smashed and cracking and I was feeling lazy, so sprang for the Van Steel 8.5" bolt kit.

1) Due to the difference in thickness between the stock, compressed-by-time rubber bushings and the new poly bushings, I only saw 3/4" increase in distance between frame and spring top with the new bolt kit. I expect the poly bushings to compress a bit with time, but no more than 1/4", so though the new bolts are indeed 2" longer than stock, if the new bushings are used expect only about an inch of lowering.

2) the 3/4" of "bolt drop" for lack of a better term resulted in a 3/4" drop at the fender lip as well. A comment in another thread indicated a 2 to 1 relationship between bolt length and body drop because of "the design of the trailing arm". This simply isn't the case. You'll see the same drop at the fender lip as increase in bolt length between frame and spring.

3) I still have over an inch of clearance between the spring ends and wheel/tire, with 245/60/15s on 8" rally's.

Worked well for my purpose, as I was a touch high in back and wanted to level the stance, not slam it. YMMV.

 

I purchased some Nolathan bushings from Summit a few years ago. A form of poly bushing. As the replacement rubber bushings I had purchased just 5 years prior had already perished. Yes they came from a reputable Corvette vendor. I believe the Nolathan or poly bushings will never compress. Or very, very little over time.
The interesting thing is that they mould these bushings just like the rubber ones they are replacing. Not the compressed rubber bushings, but rather the unloaded, uninstalled rubber bushings. Made my car resemble a 4 wheel drive.
I took them back out. Chucked em up in the lathe and machined about 5/16ths off each of them, and reinstalled.
Ta Da!
Ride height back to normal, no worries as these will never compress.
I run bolts about 6 1/2 inches long and I am lower than stock.
Ahhh, yes, those hardware store bolts with nyloc nuts.

 

After rebuilding my Differential on my 1968 C3 convertible the shop put in shorter bolts on the ends of the spring and this made my C3 looked seriously jacked up in the rear. After getting it back I noticed the rear spoiler in the rear view mirror which was not normal.

I spent hundreds of dollars having it worked on to no avail. It was when I met a nice gentleman from Vette Brakes and Products who laughed when I explained my issue to him. He reached up and grabbed a package of 2 longer bolts with the right nuts. It turned out the mechanics replaced my rear hardware with the wrong parts (and this was a Chevrolet Dealership) who screwed up the rear geometry.

After installing the bolts I was able to adjust the rear height to what ever height I wanted it at. I did everything to get my half-shafts horizontal and the results were great.

I have a big selection of Grade 8 hardware and whenever I work on anything important I use Grade 8 in place of the lesser hardware.