I would think the cost of buying another barrel with chokes compared to having the barrel threaded and buying chokes about equal and now you would have two barrels. And you could sell the full barrel to offset costs.
Buying a new barrel isn't that simple for this gun (Trap T). It is the step rib barrel and they are hard to find or expensive when you do find them. I dropped the gun a couple months ago and dented the rib. My buddy fixed it with a special tool he has but it still isn't pristine. If it were unmolested, so to speak, i would leave it as is, but since the rib issue i have no problem having it choked. If I can find a replacement step rib F or M choke at a reasonable price I would likely buy it as well.
Why Rem chokes in particular? I think it will need some sort of thin wall chokes. If it can be threaded at all. I really like my Briley choked O/U with the thin walls. The Briley thin walls are a great choke system.
I have had a couple done by Carlson's, but consider that the charge (as shown in the latest Carlson's catalog I have at hand) is $160 for Remington and that you need an OD of at least .875". They charge another $20 for return shipping and you need to ship your barrel to them, so figure another $20. The charge includes three flush-mount chokes, however. Extended choke tubes are a bit more.
They do a good job and get the barrel back to you promptly, but I agree with the advice here - buy a barrel already threaded for RemChokes and leave your full choke alone. If you're patient, you can probably find a good used one for about the cost of the Carlson's threading job and then you'll have two barrels.
Sorry - just read the second post about it being a "Trap T" barrel. Does it say "Target" on the left side? If so, the barrel may be the overbored version, which would significantly complicate the issue of threading it for chokes, because the overboring introduces .018" additional constriction behind the area of the barrel that would be choked.
I'm pretty certain that the receiver will take any 1100 barrel: you need not find another Target barrel to thread for chokes, in fact, if you wind up threading a barrel for choke tubes, you would be much better off choosing a barrel that is NOT overbored if you're not going to shoot trap with it, because the additional restriction of the target barrel will result in a tighter pattern than the choke tube would ordinarily produce. I use an Improved Cylinder tube in my 11-87 target barrel which, with the built-in restriction of the overbore, yields a pattern about like a tight Improved Modified. If I use a modified tube, it shoots like an extra full.
So - bottom line: find a nice clean used RemChoke barrel in the length of your preference and break 'em all.