I'm pretty sure you're not going to get a 240 gr. jacketed bullet going 2,000 fps, at least not in my Marlin 1894P. I've chronoed 180 gr. bullets at a little over 2,000 fps.
Here are some Marlin chrono results:
2400/21.6 grs, 255 gr. LSWC, 1,745 avg fps
(1,724 ft. lbs. of muzzle energy! Keith style bullet.)
2400/20 grs, 240 gr. LSWC, 1,657 avg fps
2400/19.0 grs, 265 gr. GC-LRoundedFP, 1,494 avg fps
2400/21.0 grs, 240 gr. Berry's FP, 1,632 avg fps
(the Berry's is a plated bullet)
I could probably get a 240 gr. LSWC over 1,800 fps. Hard cast lead bullets are going to go a little faster than jacketed bullets.
I think you are going to see about a 200 to 400 fps increase over a 4" barrel revolver. I don't think there is much of a velocity increase over going from a 16" barrel to a 20" one. The Marlin 1894P is a great length, very handy. At max you can get nearly a ton of energy at the muzzle.
I don't know about a Winchester 1894, but the Marlin 1894 will handle 40K of pressure.