Respectfully, don't do it.....

Plenty of standard rifles around that you can modify.

Pre 64's have a mistique about them, and certainly collectors are always on the lookout for good examples. Some hunters (like me) often look over various rifles for field use.

I've passed a NIB Pre 64 in 270 because as much as I wanted to buy it, mount a VX3 2.5x8 and take it hunting I knew a collector would give it the proper home and care that it needed (deserved). The thing sold at auction for $1350 only and yes, it was a collector, a guy that had no intention of doing anything with it other than packing it away and showing it to his mates occasionally.

I spoke to the guy and his view was that unfired rifles should stay that way. Couldn't help admiring his discipline.

A good 375 in Pre 64 is a marvelous and relatively rare beast, it should stay the way Winchester made it, unless it has already been modified and thus is less than original condition.