The .45/70 is a very old design, lots of better rounds out there. I'd go for a bolt action, Winchester, FN, or Mauser surplus,to name a few. 30-06, .270, 7mm are good deer cartridges. I have shot hundreds of deer with a P14 Enfield .303 British, now use a .308 Norma Magnum but it doesn't kill 'em any deader than the ol' 303. The magnum is more for moose and elk, but works on everything from muskrats on up.
If you're set on a lever action, get a Browning BLR or a Savage 99. .243, .308, .250 Savage calibres are available. Check out the gun shows, but take along someone that knows guns inside out, there are good used guns around.