Randy, Janet's RR had stock caps with ARP studs at 615 hp for 8 years and never a problem. The car had a LOT of 1/4 mile passes and a Bunch of road miles and some street test n tune sessions so it wasn't babied at all. It would be for your peice of mind only that I would tell you to get new caps.
I had alum caps and studs on my car at 771 hp and I used NOS also so that is why it had them. You will have some cap walk no matter what you use but it will be less the more you do to it over stock.
just my 2 cents.
David