Does any shop make something huge like 45-120, 50-110 or 70-150 Winchester? If not whats the biggest made?

www.sskindustries.com/encore.htm

JD will make you anything you want.

P.S. the calibers that you have listed are old BP rounds with very low working pressures (around 20,000).  You want to get spanked, step up to something like the 458 mag with 50,000 PSI working pressure lobbing 500 grains down range at over 2,000 FPS.

Or if you just want to get slammed, then there is always the 460 WEATHERBY, but it’s going to leave a mark if you try it off the bench.

Hmm looks like 470 Nitro Express is the biggest bang it can take. Dang i bet it gonna hurt like a