OK, let us get this out of the way first off. I AM a #1 lover and have been for years.
The #3, while equally strong, has a bummer of a butt stock for anything with a recoil potential like a 45/70!!!!!!!!!!!!!!!!!
The #3 however, looks way cool with #1 butt wood in place, and this takes care of the bad stock shape issue.
The action lever, may or may not need to be tweeked a tad, but if so, not a big thing for a gunsmith.
With my #1s - 45/70, I found shooting even with the good stock shape, that shooting with iron sights was very painfull because of the low head position required. With a scope in place, NO PROBLEM!!
OH, and by the way, if your shooting a #3 in 45/70, even with #1 wood, install a good/thick/soft recoil pad!
Keep it coming!
Crusty Deary Ol'Coot