Before you remove the old headlamps, check all the earths from the headlights to the body. Also make sure that the battery has a good earth strap to the body.
Then as the headlight switch and dipper switch are probably 30 years old fit a couple of relays near the front of the vehicle and splice into the original wiring, or, if as I have found on some older cars I have had to replace the wiring from the relay to the headlights. Use a heavier guage wire than standard so there will be no curent drop if you decide to use more powerful wattage globes. These relays will take all the load off of the above switches and you should see a big improvement in the beam quality.
Then you can decide what type of headlight you want to fit. I have fitted H4 Halogen semi sealed beams with the new Blue Globes which give a white light similar to the Xenon lights. A 55watt globe gives the same brightness as a 100watt with the less current draw of the 55watt globe. There are brighter globes available but my guess Napa would be a first stop. When I am in America I have found them to be the most helpful and usually at a fair price.
David