Steve , the 1/2 ton trucks had shims in front of the double row ball bearing .
The 1 1/2 ton don't show any shims in the book , either in the parts or the assy .
The pinion depth must work out pretty much ok , just fitting it up .
Don't know what you can do about the worn nose , short of machining it and fitting a spacer to match. It's a bit hard to visualise , can you post a pic ?