I might be able to share some info as someone else who isn't afraid to do slight bubba work (every rifle I have has a scope mount of some kind. Some were D&T by someone else that I put back into original shape but kept scoped. And some I had scoped with original/replica mounts. I also have my Chilean 1895, M1 Garand, and k98 threaded.)
Feel free to thread it. Even if it is a USGI Barrel there is no real consequences to threading it. However, the logistics of suppressed .30 carbine is rough. The twist rate on an original USGI carbine barrel is too slow to stabilize heavy grain weight cast bullets. (1/10 I believe.) You can load subsonic for it and it can be fun, but the projectiles have to be custom made. Also a faster twist barrel is advisable. I have a 1 in 7 threaded military contour short barrel sitting in the safe at work, waiting for the paperwork on my SBR M1 to be processed. You can obviously also put supers through a can, but it wont be as quiet. Here is a picture of what I am trying to make, not my pic, but it was the inspiration.