The 465 in the SM465 stands for it's torque rating of 465 ft lbs. I think the Ranger is about the same rating torque wise.
The Muncie was used in GM's medium duty trucks with GVWR of 26000 lbs and many were abused beyond that weight wise.
I think you will be alright with the Ranger because the torque limit of it and your main box are close. Go too much over the 465+ ft lbs and something could break. I know that the SM465 can take a lot of flogging and keep on ticking. Never have seen the Ranger in action though.
What kind of "tractor motor" are you thinking of using?
Sounds like an interesting swap project.
