I wouldn't be too concerned with a cracked block. Heads on the other hand is a different story. Get them checked. If you are going to bore an engine, I say go big or go home. A well worn engine could already be at .010 over. Go with at least a .030 over. Back in the day it wasn't uncommon for hot rodders to go .100 on overbore on the stovebolts. Keith Black still offers .080 pistons. Patricks, Egge, Langdons, Clifford, and Larrowe's are all good places to start looking for performance parts. Most Trucks will have a solid lifter cam, being yours is a 57 it may have been drilled for hydraulics too. Check your casting numbers on the block and head to see what they are. Patrick's also has a good csting number guide. Anyhow, good luck.
