Bullets for the 45-70 are most likely to not stabilize in the 45 Colt as the lightest 45-70 bullets are in the 405gr range.Load data would be non existent,I resize 540gr.458 dia. lead bullets to .448 so resizing to fit in a .452 bore is not the issue if using cast lead bullets. the weight of those bullets will not be safe or pleasant in any hand gun.Barrel twist are 1:18 for the 45-70 and 1:16 for the 45 Colt. Just not enough barrel to stabilize such a big projectile.The 405 gr. is the lightest cast bullet for the 45-70 @.458 dia that bullet resized to .451 will still be in 398-403gr. or heavier. No fun there in a hand gun or load info.Buy a mold for each gun and have fun.
Saeco,RCBS are the best off the shelf molds, then Lyman and Lee in that order.There are custom mold makers in particular for the 45-70,Paul Jones,Steve Brooks,Buffalo Arms and many others.Google is your friend