Ron,
There are 3 generations of factory exhaust manifolds. The only problem is with the middle one.
1983 - 1985.1 used cast iron Manifolds. Bullet proof but heavy at 20lbs per set.
1985.2-1987 ~ or so. used stainless steel tubular manifolds with the gusset on the #1/#4 cylinder half. THESE are the ones that crack. You can repair but they'll crack again. They're light at 7 lbs.
~1988 used stainless tubular as well but they were "jacketed" all around the joints. Again, 7lbs.
These are not rare in my neck of the woods. I sell Cast iron sets for $75 and 88 style sets for $125.
We've already been thru the chips and headers deal. People were buying Stahl headers at $650, plus shipping, plus install, then going to the dyno for hours to flash their chip to get more power than other drivers.
Let me know if you want manifolds. I currently have a good 88 set in the shop.
...at your service,