[bd111]

You got good stuff there if the barrel still has good accuracy in it. Different will be able to tell you who was making heavy barrels for SAI late '70's, if anybody. Barrel could have been added to a receiver at any time.

 

[bd111]

The good news about M1A's is that, unlike with the M1 Garand, there's nothing historic or collectible about them. So if you use USGI M14 rifle parts you'll have good parts, or should. Good luck.