The 590's barrel mounting method isn't like an 870's. It has two areas that mount up on the magazine tube.
It would probably cost more to "customize" it than it would be worth.
Part #s 6 and 33 $150, total. The Mossy mag tube is Loctited in, not soldered, like Rem. Buy a new barrel and mag tube (& shorter spring), and you're GTG. Just a thought. 2" does make a definite difference in handling, but the 12" & 14" lengths are pretty cool.