Whatever you decide on is gonna be great!
As someone (River City John I think) pointed out, some of the guns were true 1860 conversions so they kept the same 8" barrel as the C&B guns. The 1851 that the 38 conversions came from, I'm pretty sure had 7 1/2" barrels. The (1860) Late issue Army Open top which is called the 1871 by Colt and has 1872 engraved by the wedge
Has the 7 1/2" barrel & the longer Army 1860 grip size. I'm not sure about the smaller (38) guns made by Uberti on the 1851 design.
Clear as mud, right?
I got an 1871 Open Top last August. It is the late model - which has the longer Army grip, 7.5" barrel, and is chambered in 44 Special. This gives me the choice of shooting 4 different rounds: 44 American (not likely because the ammo isn't available), 44 Special of course, 44 Russian - which is a GREAT option and very popular, and the (new type) 44 Colt round (my choice) which isn't much smaller than 44 Special, but is close to authentic of the era. (Alas, the original 44 Colt is a heel-based round that is actually 45 caliber.)
Go figure.
You'll love it. Major 2 is one of a
large group of us who think the 1860 Army (so also the 1861 & 1862 Colt C&B guns are, too) is the
prettiest and best-LOOKING firearm
EVER made. They have those looooonnggg flowing lines and a sleekness not seen on
many any other guns I can think of.