From the floor board to the roof, there's about 1/2 difference, The width, from inside door is amost 2 inches differance. (This is on a steel body)
Of course if you going fiberglass body, all bodies are different.
good example,, my 34 chevy is a downs body. Waynaue (screen name on here) has a 34 chevy Outlaw body, we couldn't beleive the differance in the messurements. no parts are interchangeable.
Mine is about 3 inches smaller from door to door than wayne's
You would think all fibglass bodies would use the same mold. off a steel body