The NV4500 5-speed manual transmission from '88-up Chevrolet/GMC trucks is a 'common' manual transmission swap. With the NV4500, you get a fairly low gear plus an overdrive gear.
Take a look on the forum using the search box for other write ups on transmission swaps; including: 700-R4/4L60E & 4L80E 4-speed autos & 5-speed NV3500 LD manual and NV4500 HD manuals and NV5600 6-speed manual transmissions (and others).
Additionally, you may consider swapping rear axle gears (or complete rear end) for something with a higher ratio. Really, it all depends upon how you normally use your truck. Example: If you have 4.56 gears and are normally driving highway, then you may want to go to 3.73 or 3.42 gear ratio and keep your 4-speed.