The NP435 has a 1 1/16" input shaft. Two strokes with a flat-file down each spline and the Benz clutch disk fits. I had to do the exact same thing with the Rover transmission in my other truck and it's been in there and fine for 7 years now.
By the way, the bellhousing is pretty much done. I've got to figure out the throw-out bearing arm when I get it on the tranny but that should be pretty easy. Benz flywheel, Benz pressure plate and throw-out bearing. Even the pilot bushing is pretty standard bing 1.375" x .668"
I hope to have the two mocked up and sitting in the new frame in a week or so.
I don't remember, michigandon, what transmission were you trying to use? Now that I'm at this heavy, we should talk. Send me an email.
Jim
jim@seriestrek.com