I’ve fit hundreds of synthetic stocks to Marlins, MPI and some made by another big name stock maker but unavailable to the general public. They aren’t too hard after you do a few dozen to get it figured out. Marlin tangs are shaped by a person with a belt sander so have a pretty large variance from gun to gun. This makes it nearly impossible for a stock to be a “drop in” and have any semblance of fit. So they get you close and it’s up to you to build up or cut down the stock to make a finished product.
Having done as many as I have and knowing what I do I wouldn’t want to tackle one without my mill. If I absolutely had to I’d do it with my Foredom tool but it would take longer.
If you do it don’t forget to relieve the screw hole in the butt. If you don’t you’ll either crack the stock, bend the tang screw, or both. Good luck
