Some years ago I rebarrel/restock a Rem 1902 rolling block that was in 7mm and sporterized, I used the Numrich 45-70 oct barrel and made a tang sight.
My father had a 43 cal Rem rolling-block in his basement for years, came from Hunters lodge in the late 50's, NRA poor condition. I re-worked this over by starting with the receiver, I milled off the half dovetail edges and made it square, bent the lower tang for a pistol grip, made a bushing that I could change in the breech for center or
rim fire. Best of all, I made a trigger with a sear for a nice trigger pull. I was given a blank of Calif walnut which I used to make the butt and forearm.
There is a company that sells parts: Rolling Block Parts but expensive. I can not post photos so send me an email for photos