A fine rifle indeed! I've been hoarding an NOS M70 early-50s date 270 Win sporter barrel (bbl only) for some time now, waiting for the proper use for such a beast. IMO the 3 classic M70 calibers are 220 Swift, 270 WCF and 375 H&H. Can't go wrong with any of those! 22 Hornet is also excellent but is also associated with several fine early rifles other than M70s. My last M70 270 would put 5 150-gr Nosler Partitions into less than 1 MOA at over 2950 fps and was a heckuva rifle, I hope your M70 gives you just as much pleasure.
Regards, Joe