height of 1/2 ton rear cab mount bushing

[GMC 3]

switched my cab over from a 3/4 ton frame to 1/2 ton frame, but already had the new cab and radiator bushings for 3/4 ton. installed them and the rear of my cab sits too high. i checked with catalogs and it looks like the front cab bushings and radiator bushings are identical between the two. It looks like if I cut about an inch off of my rear cab bushing the truck will sit the way its supposed to. If someone could measure the height of a 1/2 ton rear cab bushing for me I would appreciate it.

Thanks