I have a Glenn Nelson build match M1Aicon from 1982. It has a replacement barrel marked GN - 82. So that is how the M1A barrels were marked at least some of them. Validated this through an old M1A smith named 'Hook' Boutin who went through the rifle for me. 'Hook' trained Glenn in the early days.
VAlue is tough on the Garand. If I wanted a great shooter and was willing to spend $1500, I would build a rifle (actually have done that) with a new Kreiger or Douglass barrel.
Obviously it's not an original or even correct NM anymore.
For me there would be some value in having a Nelson build Garand especially since I have the M1A but it would only be a small premium.