I know that many of the parts carry over from year to year, but RockAuto has a master cylinder under the Napa brand thats says vehicles experiencing low pedal heught should use the 96' application.

The difference is 1/8" on the cylinder bore, why do they suggest this?

This is for a 1 ton pickup by the way.

 

A larger bore master cylinder moves more fluid for the same stroke, which will work out to a higher pedal. At the same time, it will require slightly more effort to build the same line pressure, although it may not be a problem with power brakes.