Zulch, I got to handle one with a 7 1/2" barrel a few years ago and I remember thinking it looked bigger than I was expecting. Purely subjective of course. In terms of any copies made, some years back US Patent Firearms(now defunct) was making a single action only version. I forget exactly what they were named (Omni-Potent?) by that company but I still see some come up for sale. A friend ordered one in nickel plated, 7 1/2" in 45 Colt but for some reason the order neve quite happened.
On the original Colts, many parts(barrel, ejector rod and housing, cylinder) were apparently interchangeable with Colt SAA's and some 1878's were cannibalized to repair 1st generation SAA's.