I don't have the 22" one, I have the full length 26" Cowboy model. I much prefer the full length magazine, too.
I think the .45-70 shoots really nice out of my rifle. Recoil is pretty low, and more of a push than a kick.
There are a few people doing full magazine conversions, I believe. Wild West Guns comes to mind. However, I think you may find the conversion cost to be prohibitive.
Let us know what you find out?
~Robert
Denver, CO