i know a couple of gunco members are looking for 20" a1 gi type barrels.
well JSE has some wilson 20" a2 stripped barrels in stock for $130
the a2 is only a little "fat" only on the muzzle end sort of like a m4 but longer.
the only problem putting one of these in an a1 build is they have a .750" on the gas block.
the old a1's has this little .600" & somthing gas block.
there are lots and lots of .750" gas block pulls floating around --so finding one shouldn't be a problem if you go with the a2 barrel. Wilson Arms 20" Government Profile 1x9 Air Gauged Stripped Barrel