You need a finger lever and trigger plate. The finger lever from a 336 will not work. I don't know if a lever from a 444 will work or not so make sure you get one for an 1895. Here's the catch, Marlin/Remington won't sell you the trigger plate and they say the lever for a 336 and an 1895 have the same part number (I called them). You could order the parts from Western Gun Parts in Canada, but they might sell you a lever from a 336 and tell you it's for an 1895, (they did this to me and they weren't interested in making things right).
As for why to do it - I completely understand. I wanted a GBL but didn't want one made by Remlin. So I took a JM stamped 1895G, converted to pistol grip and added the extended mag tube from a GBL.