Good info from oldbogie and MAN! does he ever write a book when he answers a question
Anywho I have a 507" Cadillac that I just finished building, going to the dyno cell at the end of the month. The Cadillacs were built to run at 3500 rpm so the reciprocating parts didn't have to be forged. The worst thing is the castaloy rods and the rocker arm assembly. The crank is nodular iron and pretty much bullet proof...for a pretty warm build.
Obviously there's not a lot of hipo parts so you either buy very expensive forged race type rods @ $600 or use the PEP 4340 forged rods with ARP cap screw bolts. On the MTS and Cadpower forums many members have used the PEP rods with good results........so I bought a set from Falcon Global on ebay for $220 shipped.
Now being the skeptic that I am and full well knowing that these are "off shore" I polished the beams (length wise) had my machinist work them over....mag'd, clearances checked, re-sized the big end and run them through a real shot peen cabinet, not just bead blast them as some shops do and call them shot peened. He said they looked like a decent part, the dyno and time will tell. BUT, if you're building a small/big block Chevy/Ford (you didn't say) I would go with the good Scat rods, they have a great reputation and are "usually" ready to go out of the box but I would get them checked also......ok, geeeez now I'm writing a book.