Reading through there catalog again and found a interesting paragraph on there chevy short block assembly. "Also available are premium quality ARP fasteners, as used in complete World engines" So I guess the spec. sheet I got with my block was correct it states main studs 1/2"-13. And if I would have bought a complete engine it would have had ARP studs,maybe.
I should have read the chevy spec. sheet and read between the lines also. I'm just changing mine out before machine work just as Paul would say to sleep better at night. $ 125. bucks down but thats just a drop in the bucket for this build.