You can still get GI/surplus 30-06 ammo for the CMP for somewhat reasonable prices, and there are commercial loads available for it that shouldnt be an issue.
They also make an adjustable gas plug for the M1 thats supposed to allow shooting the heavier loads without damage. I ve never used one, but a number of others here seem to approve of them.
.308 can have the similar issues too, so you have to weigh that as well.
Personally, Id just go with one in 30-06.