Filson, I'll attempt to answer your question but someone else may do a better job a little later.
The 37 original motor is a 207....the 36 was a 194, I think. They will pull the gross weight because they are geared for it but along with the gearing comes a slow speed. Probably 45 MPH would be an educated guess....and then you have to STOP it!
Unless you have a neat original the first things you'll probably wish you had done was step up to a nice 235...or larger, and also you'll be wanting a higher gear....which means you'll need better brakes. I think you see what I mean. So, do some planning, and the more complete, running truck you find the better you'll be...even if you have to pay a little more.
Hope this gets you thinking in the direction you need to go.
