My '81 will shortly return from paint. That means I will soon have to remember how I took it all apart. Something I've been wondering has to do with screws, which kind and where they go. How have others handled the myriad of fasteners issue? Buy a boxes of stainless screws, one of each size, and just use what seems right?

Don't use stainless screws. Use a good quality zinc plated, and make sure they are at least 8.8 grade. Most suspension bolts will be 10.9, maybe some 12.9 stuff, not sure if the fiat has any of those ...