i started tearing apart the 350 i bought to rebuild. i removed the oil pan, and found its a 4 bolt main. i think that excellent considering i only paid 75 bucks for it. it ran when it was pulled out of the truck it was in. internals really dont look too bad. no major sludge issues, no major wear, that i can tell so far. i have to remove the heads next. i think im going to tear it down to the bare block and take it to a machine shop have everything gone threw and see what i should replace. i want the block hot-tanked and magnifluxed for cracks. the heads will be rebuilt, a new cam and lifters will also be installed.