GMC and most other vintage engines use hardened rod and main bolts, so unless your bolts have been grossly over-torqued, they can be re-used any number of times. ARP has nothing acceptable for replacements (I've checked). Even if they did, you would be changing the rod bolt "imprint" or contact patch, and the rod would no longer hold a torque setting. Experienced engine builders can tell when a rod bolt has stretched. The torque wrench has to be moved an excessive amount to achieve the specified torque. That's the sign that a bolt is no longer usable, but it's rare on a GMC unless the engine has been rebuilt by some oaf with an impact wrench.
If you're really concerned about the integrity of your rods, spend your money on having them magnafluxed, sized and shot-peened. But this can open another can of worms, if the peening is done incorrectly it can ruin a set of rods. Find a shop who knows what spec to use on your rods. If they don't know what "arc height" is, try another shop.
Head bolts are a standard size and you can get replacements from Gardner-Westcott co. Must be grade 8 but GW even has them chrome-plated.
