How big is a box?

[76D100]

I need to know the size of the inside of a step side box, preferabley the dimentions of a long one, but the main size I need to know is how wide the inside of the box is. The sooner I know this the sooner I can order my diamond plate for the bed.

Thanks guys.

[77Utiline]

Usually about 54" wide. Bed length varies 6' (sb) to 8'(lb)