My 51 1 Ton has the 14" drums on the rear and I have no issues with a 16" rim. The only problem with the 16" rims seems to be on the front because the setback causes them to hit the tie rod ends. This problem has been discussed at length but I don't recall any mention of a problem with the rear.
Changing out the rear drums would be quite a job and I don't know how one would go about it. There would have to be a backing plate from a donor that could be adapted to the axle. It is probably more feasible to change the whole axle. In my case I am only going to change the pumpkin out for a better ratio.
That was a lot of good information about the serial numbers and all. I have never checked for numbers on my axle.
