Any of those barrels will fit on the super magnum gun, in fact, any 870 barrel will fit. The only difference is the receiver stroke whether it is 2 3/4, magnum for up to 3" shells, and the super mag up to 3 1/2". The only reason they don't list a 3 1/2" barrel is because they don't make a slug barrel with that long of a chamber, but the 3" barrels will work on the super mag, just be sure not to shoot a 3 1/2" shell thru that particular barrel. Between the hastings and remington slug barrels, I would get the hastings as it usually is the most accurate but then again they all differ. Good luck.
SuperMag