The 444 and 45-70 for ends ARE DIFFERENT, but you could modify one to work. there is a large "bulge" in the feed tube of these two to allow feeding the mag tube, becasue of the larger diameters. So the fore end wood is opend to all this.
OR, you could slim yours down. I too have disliked the fat forends on the Marlins. its really the only fault i can give a Marlin. I have slimmed a number of mine down. Take your time and work slowly. be sure you keep everything even and continually check thicknesses. You can safely take quite a bit off 3030 and 35 rem forends, less from the 45-70 and 444.
CW