Bolts from GM will cost you an arm and a leg, even at the local hardware store, but its cheaper there. This is what I did on my 69 Z 28..
All Suspension and frame bolts I used Grade 8, Whats a grade 8 bolt? Well, You count the number of lines on the head of the bolt and add 2.. that will give you the actual grade.
on all engine components I used Grade 8 Black Anodized then painted Socket head bolts, this is a detail thing here. Stainless steel is good also, but I just found that the Socket head bolts made it look better, I cut holes in a carboard for all the bolts to go in it, and painted them over with High Gloss 500 Degree Satin Enamel paint.
I think the only stainless steel bolts I used were of a socket head type that holds down the intake manifold. Also, If you notice on the harmonic ballencer, and crank shaft, the threads are fine, I re-tapped my ballencer holes, and crank shaft for a course thread fit, so that it can properly tourqed down without stripping. Anymore tips just ask.