Some parts that we used to use would be crazy to use now the perfect example wold be connecting rods. By time I paid to change bolts, resize, balance, magnaflux, shot peen, I would polish the beems, usually bronze bushings for the piston pin, and cross my fingers they would last. We had to over cam to make up for lackluster head flow and for some reason they loved over carbureted. A Friend of mine is doing a build like this as we speak but pretty sure he will be using Stealth heads. 906 heads worked back then but by time you upgrade the valves, bronze guides, port, true up the decks, magnaflux for cracks it adds up to a lot of money. Stealths max out at 267 cfm stock on my bench and go 300 cfm plus with minor porting. Make your choices wisely.