My buddy found an old API Alumi-Lock treestand burried under years of brush and leaves. I has the fabric fold out seat but is ripped apart. what kind of material would be suitable to trust my 205lb butt on, and withstand the conditions?

Nylon or canvas,and if you DIY, the stitching is what you need to pay attention to.

for the sense of safety, I may check an embroidary(sp) shop to see if they can do something.

Do yourself a favor, order one directly from API. I think youll be much happier. API makes some pretty great stands and their customer service is awesome