It was never offered on a production basis,but the pre_64 M70 target rifle could be had in 308, by special request(not to be confused with special order) starting in '59 or '60. I've seen standard targets in .270, 220 Swift, and.243 on auction sites and photos of a .308 on another forum.
Oddly enough, the.270 chambering was a standard option up till 1949, IIRC.
I've read that Winchester would make you one in .222, .222 mag or .300 Win Mag if so requested but have yet to see one.
BTW, that's a nice looking bull gun. What year was it made?