Advocate - I'm gonna stick my neck out here for a bit regarding that Marlin 336 in 44 Magnum. The 336 was designed as a longer action to handle the longer cased rifle calibers whereas the 1894 was designed to handle the shorter pistol calibers. I think (that is, I think that is what I have read previously about the difference 'twixt the two).
I think the 336 in pistol cartridge chamberings was discontinued because of problems encountered by trying to load and chamber short cartridges through an action originally designed for longer cartridges; but again, I'm not exact-a-tively certain about that. However, as a direct result there may NOT be any advantage to a 336 in 44 magnum as the Marlin 1894s are known for their strength.......
Can ya'll shoot 44 magnums in a 444 Marlin. I have. Beartooth Bullets will tell you it can be done and they have done it, as well as shoot the 44 Spl and the 44 Russian from a 444 Marlin. Some folks say 'No', because the case size at the base is smaller than the 444 Marlin but when I fired 44 magnums through mine I didn't see anything that would indicate case stretching at that point. You would have to load them single shot but it can be done. If you do, becareful not to leave a lead ring in the chamber that would adversely impact the chambering of the 444. HTH. Mikey.