This has been pretty much said but I will gel it down a little differently.
The pressure signs you are requesting are warnings that you are dancing on the edge.....with a modern rifle of bolt action strength.
These signs occur at pressure levels well beyond the working pressure level of rifles many other rifle designs.
You might be able to load till you see some pressure signs in a Siamese 98 Mauser 45-70 or in the Ruger #1,though I doubt the 45-70 brass is rated for the sort of pressures that flatten primers,etc.
Your plan is not a good plan.You can do as you choose,but your plan is not good.
I suggest you find out the recomended max operating pressure for a 1895 Marlin in 45-70 then approach that max pressure with due caution.
Years past we did not have so much published pressure data and software like QuickLoad. Your venture is unnecessary.
If I had to guess,this is the result you will get from hotrodding:
The brass supported by the chamber will obturate and grip the chamber.
Some spring will occur with the lockup of the lever action,and the bolt face will move to the rear a few thousandths.
Right at the chamber mouth is where all the stretch of the brass will occur.The brass will thin at a stretch ring.At about the second,maybe third reload you will have weakened brass.
At some point,way up in those high pressures,the case will rip in two,and that hot gas will look for your face.
Or maybe that big bear will need a second shot,but when you jack the action only the rear 3/8 in of the brass will come out,the front part will stay in the chamber and your rifle will not work.