I have a set of Dick Cepek Norseman radials on my M38A1. 235/75R15 is just 1/2" shorter than the stock 700x16 NDT. They work really well compared to bias ply, but I believe those went out of production some time ago. A replacement I would lean to would be Cooper Discoverer L/T. 215/75R15 would fit your rims and should fill the wheel wells without getting out of hand. Narrow is good for snow, wide is good for sand/mud. Radials do outstanding on rocks. Always thought a tractor tire tread looked way cool on a flat fender, no idea how they perform.