I was told my compressor is bad. I was thinking of switching to R-134 but was quoted 700.00 plus to replace it. The AC guy said I should just stick with the R-12. Because I would not be happy with the R-134. Any advice about what to do?

If the compressor is bad, it doesn't really matter what type of refrigerant you go back with, you still need a compressor ! Maybe your A/C guy wants you to spend the $$$$ on R12 because it's about $30 a can!!
There's no reason to go back with R12 anymore. You can replace your compressor, flush the system, and replace the reciever/dryer, and go with the 134. True, the 134 doesn't cool as well as R12, but it will work OK if the system is in good condition, and all parts are working right.
The best way to go is with a new compressor, not a reman., especially the R4 that you have. They will cost more, but well worth it in the long run. Check out some of the other threads here on this subject!

My two cents.....

I recently went through the changeover on my '78, worst part was replacing the buried accumulator, which is no sweat on yours. The cockpit on a 'Vette is so small the inefficiency of the 134 compared to R-12 is negligible. The DIY cost is under $250.00 including the compressor, accumulator and all parts. There is an extensive thread on it at DigitalCorvettes.com. If I can find it I will post the direct link to it. R-12 is an obsolete moneypit!

Dave

Skuuuze me!!! The extensive thread on it was here! This is the thread I was referring to;

http://www.c3vr.com/forum/forum_posts.asp?TID=58378&PN=2

Also I noted you had a C-3 not a C-4, the C-3 is a pain-in-the-butt to swap out the accumulator on, but doable.

Dave

Clickable link

That thread looks VAGUELY familiar....

Buy a complete new system from Hot Rod Air.  It works well and it is guaranteed.