There was a huge thread where the grandlordkhrome or whatever his name is over on SF actually took one of these manifolds and X-Rayed it. Then he tested the metal content and quality. Found it was a pretty dang good deal for the money. It is 321 Stainless. Low grade, but it qualifies as 321.
Welding is somewhat poor, but nothing a quick pass over the top of each bead would not solve with a simple mig feeding stainless wire. (Get wire that is designed to weld 321, and your golden.)
Braces and flange repair/porting is also a simple fix. Patience and a large belt sander will solve your flange being warped. (They have these at machine shops, or you could pay to have the flange machined flat, but the belt sander works just as well.)
I've decided that after the bills are paid off on the Supra, about next year sometime, then I'm going to pick up one of these 321 manifolds, make a pass over all the welds with my mig and the right wire, weld up the inside of the ports to clean up the crappyness (is that a real word? It should be.) and port everything nice and smooth where possible.
Then the whole deal is getting sand blasted, and thermal coated. (I'm going to build braces for this manifold, both welded into place, and bolt on that use the stock mounts, with custom hardware/brackets to further support the turbo/manifold.) It should be pretty crack resistant, and allow me to upgrade to a GT4088r turbo that I've been wanting for awhile. It's tempting to cut off the T4 flange, and re-attach it with a slightly new angle, placing the compressor housing further from the runner, and pointing the DP closer to the manifold. This "twist would be further enhanced by a "slope" so the turbo is sitting nose down slightly, making clearance for the intake and IC pipes to cross over the top.
I think by tucking the DP closer to the manifold, there will be more clearance for a 4" design that I want. The idea is to have a 4" inlet pipe, and 4" DP. From what I've seen, this setup should really rock, and I'm looking forward to doing it next year.