my truck had a 3 window cab , I since found a 5 window in much better shape. my truck is registered as a 51. Changing the cab theroretically could change the year model ? No ID. plate. . .
From an ethical and maybe even legal standpoint, you should be able to simply use your body (Vehicle) ID plate on the "new" cab (as long as you legally own both cabs).
What year is the cab you are considering using?
If you interested in reading "too much information"
here are some year-differences "factoids" accumulated from various websites, documents, and articles.
This article from the LCVA is especially comprehensive (
LCVA - Light Commercial Vehicle Association, which later became
This Old Truck, and now
Vintage Trucks).
