Take it from my experience..
You can easily upgrade your headlights from sealed beam to modern day lamps without chopping up your factory original headlamp wiring harness.
Easy to revert back to original should the car be sold,or swap into another car.
In my 73 Satellite wagon,I used the Putco 100 watt headlamp wire harness.
Plug n play.
Take the load off the headlamp and foot dimmer switch since it has two relays in the kit.
I replaced the old sealed beams with Hella headlamp conversions.
H4 for the low beams,and H1 for the high beams.
I upgrade the bulbs to the PIAA Exteme white bulbs.
Much brighter at night..When the highs are on,I have a total equivalent of 400 watts of light!!
When the lights are off,they look kinda stock and look better than the blingy plastic headlamps street rods and custom guys are using.
All the parts I used were available from my local auto accesories/speed shop.
Hope this helps.
Harness:http://www.putco.com/products.cfm?action=ProductView&Id=9ac2e1d3-e255-4107-d1d4-9273fe4298ef

Headlamps:http://www.rallylights.com/hella/HeadlampsMain.aspx