I replaced my original non synchro trans with an SM 420. I had to coordinates the bell housing, starter, flywheel and shorten the driveshaft. I may be mistaken, but the bell housing for an sm 420 may bolt up to your 216. I was working with a 235. You may also have to deal with the clutch and brake pedal mounting. You could do anything from replacing the engine trans, and rear end for more speed to just learning to double clutch. If I remember correctly 1937 or 1938 was a year of change for the 216. You should probably confirm that you have the original engine. It is possible you may have a splash oil 235 or even a new 235/216.
