[68Timber]

Lowering the truck to a 2.5" lift "should" help, right? You're getting the truck a little bit closer to the tires and hopefully it'd help with wind drag under the truck. But I wouldn't install a 2.5" lift unless that's the lift you really want because I don't think it's going to fix the problem you asked about.

Like everyone else mentioned, the truck has the aerodynamics of a billboard and the TBI 350 wasn't a powerhouse. The truck's already been regeared properly for the tires, the only sure fix now is horsepower, or more accurately, torque.

I don't mean to be a killjoy because I love your truck and I'd DD it but if it were me I'd leave 15 minutes earlier every day, slow it down to 72 or 73, and enjoy driving a badass truck.