I agree with the mob on porting a 45-70...not needed and adds noise to the shooting event. I picked up a blue #1 in 45-70 about 3-4 years ago on Gun Broker that had less than a box of ammo through it. As the story goes, the dealer sold it to a new hunter. He fired it a couple times with Remington factory ammo and reported it kicked too much. Had the dealer install a limbsaver recoil pad...still kicked too much. Swapped it with the dealer for a 30-06 (hmm, let's discuss recoil), then I won it on auction.
I love it! It has been my hunting rifle since for the PA backwoods. Recoil is moderate but very controllable. I started with 405gr bullets at "Ruger/Modern Rifle" power levels. Fun, but abusive. I'm now settled in at 1400fps. I've been watching for Stainless 45-70's for the inclimate weather days afield. Found one currently on Gun Broker, but it is magnaported....no bid from me.