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The 48 & the 1100 & 1187 are totally different animals with different operating systems from different eras.
I own some 870s & some 48s, and here is what I have discovered, It's possible the trigger group might be interchangeable, otherwise there are no parts that are interchangeable except the magazine cap. This also allows you to add a mag extension.
A while back, I found a Mohawk 48 which had a bulge at the end of the barrel. I cut the barrel at 18 1/2" , added an extension for an 870/1100/1187, and I then ended up with a decent HD gun.