Gdbyrd,
Put a brake on the 45-70 and use it for all hunting.
I own, have killed deer with both the .308 and the .243. It sounds like you don't like the recoil. I don't like it either! The .308 without a brake HURTS. Yes, it is not much more than the .44mag. But, I think the 44mag hurts. At what range are you going to be shooting the deer? The .243 might be questionable at 200+ yards. But, at 50-100yds all of my shots have been complete pass through. Don't use a 55gr bullet. Get the most common offering, the 100gr bullet and it will do all you need. The .243 is much easier to shoot and the ammo is in every store. I have, and still, used the .243 in rifle and pistol for the last 40 years. It has NEVER let me down.
Get the .243 you want. Pick the right bullet. Wait for the right shot. You will have meat in the freezer.
Bill