Well, I think I finally figured out what combinations are going together, and what motor is going where: 350 4-bolt main 1978 truck block, cast crank 10/10, bored .030 over with hypereutectic flattop pistons, Comp 270 duration/.470" lift cam, gear drive, 186 casting Camel hump 64cc chamber heads with accesory holes, 1.94 intakes valves, Z28 springs, hardened seats, roller rockers. Topped off with an Edelbrock Performer intake. This will go into my '76 Camo Blazer with 4.88 gears. SB400 2-bolt main, bored .040 over, cast crank, hypereutectic flattop pistons, Comp 280 duration/.480 lift cam, Cloyes gear drive, 041 casting 64cc chamber heads with screw in studs and guide plates, 1.94/1.50s, Z28 springs, Erson roller rockers. With an Edelbrock Performer RPM intake and 625cfm carb. This will go into my Blue '84 K5 with 35's and 4.10s. 454, 1976 block bored .030 over, flattop pistons. This is currently a running motor I want to make the following changes to: Comp High Energy 268 cam (and new cam bearings), and possibly a Pete Jackson noisy gear drive. I have the 781 open chamber (118cc) oval port heads that came on this motor... but am debating using the 215 casting semi-closed 101cc chamber heads that I have instead. This motor would go into my '82 Stepside with 4.10s running 36's and 39.5's. If I use the open chamber heads on this 454, the closed chamber heads will go onto a 496- and vice versa. Most of my reasoning for using these parts I listed is because it's what I already have or was able to get through a trade. On the 350 and the 400, I have the option of spending an extra $100 cash on each motor and having the cranks balanced. Anyone think I should have either motor balanced?