The first thing that will help your headlights is to attach the harness ground wires to a common ground, that in turn connects to the engine block where the negative battery cable bolts on. The factory arrangement of grounding to the sheetmetal was marginal when new, and barely works when old and deteriorated.
The next step up is the addition of headlight relays. The process is relatively simple and inexpensive. The benefit being the headlights receive full battery voltage from the relays, and the headlight and dimmer switches last longer since they no longer handle high amperage loads, they simply turn the relays on and off.
Here's a thread that explain how perform the install:
http://67-72chevytrucks.com/vboard/showthread.php?t=387693&highlight=headlightThe addition of relays makes a world of difference in light output, and if you still run a generator, the lights will no longer brighten and dim with the speed of the engine. With relays the lights remain constant regardless of engine speed. If you drive the truck much at night this should be a must have upgrade.
If you want to upgrade to halogen sealed beams, you should really rewire the headlight harness with 14 gauge wiring. The factory harness came with a 14 ga high beam circuit, 18 ga low beam and 20 ga grounds. This is inadequate even for stock lights, and should be upgraded to 14 gauge throughout if you ever want to run more powerful bulbs.
