I Have a 1995 chevy 2500 picKup 4x4 with LT 245/75R26 tires. 5.7 liter what the rpm. supposed to be at 75 per hour

 

We would need to know what the gear ratio in the rear differential is in order to tell you RPM at a specific MPH.. Is it a 3.73, 3.42, 3.31? There COULD be several different factory gear ratio's available, and then again someone could have changed it out along the way to something other than factory. There are gear/rpm/mph calculators available on the internet once you know the gear ratio.