I currently have a Winchester 94 Big Bore 375 Win and it’s awesome woods gun for deer. My eyes are going and I don’t want to tap my Winchester for a scope.
  I’m looking at Marlin 1895 & 1895 Guide in 45-70 and 1895 in 44 mag. My longest average shot is 80 yards, average range is 50-60 yards. I have a few spots I can get 150 yards. I mostly hunt in the woods vs open cleaning. I want to put a nice low power scope. 45-70 vs 44 mag?

The .45-70 Marlin gets my vote!

Unless your eyes are really bad, there is another option. A Marble's tang mounted Peep Sight, and Hornady Leverevolution ammunition. Gives you the ballistic performance you need out 200 yards pretty easily. It practically doubles your sight radius and works just like your peep sight on an AR15. My '94 sports one and it is one of my most favorite guns to shoot.

either will serve you well for deer.  I have a 44 lever and a couple 45-70 levers.  Use the right ammo, practice, know where your rounds hit, life will be good (except on the receiving end!)

I have owned both the Marlin in 45-70 and the Marlin in 44 Mag. My son now has the 44 mag and I still have the 45-70.  My friend has a Henry all weather in 44 mag. Any of these are a nice rifles, however 45-70 ammunition is considerably more expensive if you do not reload. Check availability of ammo.  Even if you do reload the brass for 45-70 is spendy.  I'm a big guy so recoil is not an issue with either one.  I had a standard length 2-7 scope on the 44 and a Leupold Scout scope 2.5x on the 45-70 and at 100 yds both are satisfactorily accurate.  If you use a 45-70 the scout scope is a better choice, where the 44 mag has less recoil allowing traditional optics. If I were to buy one today I would buy the 44 mag for two reasons first is the cost of ammunition and second is that the 44 mag holds more cartridges.  Either one will put deer down.

Dude, are you sure that 375 isn't already tapped for a scope?  Two small screws on the front end of the receiver, and one on each side of the rear of the receiver near the locking lug? The big bore' werent all that "early" (1980's?) and Im surprised its not already factory tapped....

If its all 80 yards and under, I'd go 1894 in .44.   Its significantly lighter, and still reliably drops deer out to 125 yards...  45-70 is definitely more  powerful, but you're mostly just killing the hillside behind the deer.  And those 45-70 cartridges are about twice the price....

I'd go 44mag because of your distance. -70 is just overkill. Wasted weight, size, noise, recoil, cost.

The only major reason I see to go -70 over magnum is that you can't find it local and don't reload.

I ordered the Marlin 1895 Guide.

You chose wisely......

you consider a marlin 336 in 30-30?

You made a big mistake. Your hunting deer at 100 yards and you got a 45/70??  LMAO.. Have fun, after the first box of ammo you'll understand.

Is SC a straight-wall cartridge state?  I ask because your 375 is, as are the other two calibers you asked about.

If you will only ever use it for deer under 100, I would definitely say go 44mag.  45-70 will obviously get it done, but the added cost and recoil aren't worth it.

For that range, your shoulder will want you to shoot the downloaded Remington 405 gr Load. The .45-70 is one of my favorites as is the .44 Mag. At those ranges, .44 gets my vote but you already got the .45-70 and I can't say you chose wrong. No tracking necessary and if you handload, you can download it.