I just came from a car show and saw several 1950 to 1953 Chevy trucks

Even though a lot of these were modified in different ways, the one thing I noticed was the difference in the gap between the cab and the bed. Is there a "measurement" that "should be" or do they really vary that much?
I'm building a 1952 chevy truck.... frame-up, and I want to make sure I get it right.
Thanks for your help! Monica