Both the 45 Colt BC carbine barrel barrel and the 410/45Colts are 20" long, the 22" 45LC barrel in the acc list is a typo. The 45-70 barrel is ~.800" at the muzzle, the Colt carbine barrel is ~.715" at the muzzle, beside being 2" shorter, it's a lighter contour. The 45-70 barrel uses a screw to mount the front sight, the Colt barrel is dovetailed front and rear, so they won't use the same sights, although it is drilled and tapped for a scope mount or Williams peep, can't really help ya on the front sight, but the Peep and Firesights link in the FAQs shows what's needed for the 45-70 barrel.
Tim