It definitely strikes me as the sort of thing that's only possible with pistols and longarms (and maybe automatics, though I don't know why you'd want it on those since they have FA options), though.
And here's the automatics version
Gilboa SnakeI've also seen someone stitch together left-handed and right-handed Ithaca Model 37s for a double barrel pump-action shotgun before. It was both comical and intimidating at the same time.
