If it's still the original rearend, most likely you have 4.56 gears. There really isn't a cheap fix for getting the rpm down, there's really only 3 ways to do it. 1, bigger tires as Hot Rod John says. Of course, this will get into changing wheels to be able to get a large enough tire with the right load rating, most likely a 16", plus the cost of tires. 2, overdrive transmission. Again, can get pricey depending on what trans you use. Another way with the trans is an add on overdrive, like the Ranger Overdrive from Advance Adapters or a Gear Vendors, but they are very pricey. 3rd option, swap the rearend gear. Unfortunatly, there really is only 1 option if you keep the stock differential, and that's the '68-'72 4.11, which was found mostly in V8 automatic trucks. High demand/low availabilty is the hangup there. You could also swap the entire rearend if you're not concerned with keeping the truck original, there's plenty of late model rearends for 3/4 ton with 3.73 gearing, this would be the cheapest way to go.
