So I've read up some more on the difference between standard 30-06 and M1Garand spec 30-06. That reading combined with info in some of the posts above indicates the difference does not seem to be the chamber pressure, but the pressure at the M1 Garand's gas port further down the barrel. Thus, both types of 30-06 are subject to the SAAMI standard of 60,000 psi max chamber pressure. Is my understanding correct?
If this is the case, it seems I do not need to limit my ammo choice, as long as the round will safely chamber (depending on bullet weight). The chamber and bore have been checked out and there were no safety concerns.