Nice find, for sure! Finding an original A4 barrel to replace the chopped one would be a real trick, but you made out like a bandit. Definitely restore it.

I've seen what appear to be NOS A3 barrels without the front sight installed, and parked in that area. I'd look for one of those first. It will always be a "parts gun", so...who cares if the barrel is not an original A4. Can't remember seeing an original A4 barrel on the loose.

Mike