Does anyone know the measurements of short vs. long bed on a 1991 4X4,I have a 77" bed?And also,does a 4X2 bed work on a 4X4 body?I appreciate any and all help.Thanks.

 

Long beds are 7ft long (84 inches) short beds are 6ft (72 inches)
(from deathcougar himself)

A 4X2 bed will work, but the 4X4 bed wheel wells tend to bulge out more (bigger tires).

 

I measure from the top and got 77".Am I measuring wrong?Should I measure from in side the bed?And when you say the wheel wells bulge out on a 4X4oes that mean there is a difference between the two?

 

The 2wd box is slightly narrower at the wheel arch, the 4wd box side is wider at this point to allow for the larger tires used on them, the difference is subtle but noticeable, though you might be able to get away with it it would look wrong. The 4wd box has a much beefier appearance. The difference is very noticeable on the 84-88 trucks if you wanted to get a feel for the differences.
The inside bed dimensions are 6' and 7' respectively with the tailgate up.
Measureing along the top you'd be a few inches longer.