Hate to be the bearer of bad news, but no you cannot. This is a total Shimano system approach and no other derailleur to my knowledge will work. The shifter, rear derailleur, r der. cable, and freewheel were set up to all work together. Assuming that this is a 5 speed set-up, the secret is to shift it into the middle (3rd) rear freewheel sprocket. There is only one adjustment screw inside the body of the rear derailleur. You want to center the rear derailleur vertically directly above the 3rd cog. If I remember from about 100 years ago, turning the screw clockwise moves the rear derailleur up toward the largest rear cog, and counter-clockwise down toward the smallest cog. Once you have the rear derailleur correctly centered over the 3rd cog, it should work quite flawlessly . Good luck.