The only real difference between the M50 and M51 is the M51 came with a checkered stock and cost more. I agree the FN style safety can be a bit of a snug fit under a scope but it's never been enough of a bother to me. Frankly, you don't have to cut the barrel to do a crown.
I have a few of those J.C. Higgins in the M50 configuration, one having been redone as a custom 7x57. The rest are still in 30-06. If you're going with a different scope set up, what do do plan to do with the Weaver bases. The M50 and probably the M51 have an oddball screw hole spacing on the rear bridge and I could use a set of the Weavers.
Paul B.

Our forefathers did not politely protest the British.They did not vote them out of office, nor did they impeach the king,march on the capitol or ask permission for their rights. ----------------They just shot them.
MOLON LABE