My first bolt action was a Rem 700 .308 like RayB's, about the same age, though a few years later than Ray.
IMR4064 is THE classic powder for .308 but R15, Varget and IMR4895 work just as well. Standard twist for the .308 is 12 but many are 10.
I eventually sold that first Rem but replaced it a couple years ago with one exactly like it, an ADL of the same vintage, late 60's. Its shoots as well as the first one did all those years ago.
In my M40 clone I shoot 168 SMK's ahead of 44grs of Varget and get sub half MOA when I do my part.
Varget is hard to find but last time I saw some I got about 5 lbs of it so set for now. R15 I have not seen for a couple of years.