Regarding the M70 pre-64 bolt, you need to find one that allows for the correct headspace - or you could be in for an expensive gunsmith job to set back the barrel, ream the chamber, or machine the bolt face.
Basically the manufacturing process back then allowed for some machining tolerances that stacked up.
The Winchester factory assembler had a bunch of bolts. He would grab a gun, insert a bolt and check go and no-go. If it worked, they would then stencil the bolt with the gun serial number and off it went.
If the headspace was too short or too long, the assembler would grab another bolt from the pile of “short” or “long”, until he go one that worked. Then stencil.
I posted a story in here a few years with a mismatched M70 pre-64 bolt that created unsafe head space. Out of pure luck, I found the bolt from my gun (SN) on eBay. The owner was selling it (parting out), as the M70 he had wouldn’t even chamber factory loads as his HS was too short. Long story short, he had my bolt and I had his.
Near as we can figure, the original owner of both guns swapped the bolts out inadvertently and then sold them.
