The clearance between the floor panel cross support and the frame at the rear mount should be 49/64" to 53/64" (that's a smidge over 3/4").
Near the front mounts, the clearance between the bottom of the floor and the top of the frame should be 1 53/64" and 1 57/64". (that's a couple smidges over 1 3/4").
You either have some more measuring to do, or you have a much bigger problem.
You need to have the cab located correctly before you even think about attaching the hood and fenders.
Errors, even slight ones, will be magnified twofold by the time you get to the front end of the front clip.
