would you use main cap bolts of unknown origin?
 

Just wondering

Here's what I would do. After checking for cracks, install them and see how good or bad they fit. If they are deemed acceptable get the block line bored.

Shouldn`t need a line bore for bolts.

I would have a good look at em.. Check the head to see if fools mistreated them, check the thread condition, and, if you can find the specs, check the bolt length to see if they`re not stretched beyond their yield.

Course, new bolts ain`t high $ either.

Were they actually main cap bolts, or just some bolts you want to use for main caps? I would not use a bolt that was not designed for main caps.

These are a factory set of 4 bolt main cap bolts with the shoulder under the head. I bought these from a PY member some time ago . In appearance they look good but, with anything so old I'm wondering ( short of magging) if they would suit a 525-550 hp street/strip engine w/o issues. The block was lined honed years ago using the original caps and bolts .Those bolts were lost and these are a replacement. Thanks, Mike

Factory hardware is of high quality.

I doubt they've been torqued down more than a couple of times at the most during their life.

I'd use 'em in a heartbeat, just like I'd use the original main bolts on my '64 421 HO rather than replace them with new aftermarket bolts.