I will give a second vote for the factory, non-halogen bulbs. These cars had good headlights when new. Most of the problems with dim lights as the cars aged was due to poor grounding of the core support, corroded connections in the firewall plug, corroded terminals for the dimmer switch or corroded terminals in the light switch. All of these problems are easily corrected. You are off to a good start by bypassing the load on the firewall plug and the light switch with new wiring to a relay. Run a ground strap from the core support to the ground lead on the negative battery cable. Use wiring from the dimmer switch to activate two relays, one for high beam and one for low beam, replace the dimmer switch and plug if necessary. It takes very minimal amperage to cycle the relays. Run clean fused power to both relays for the headlight load circuit, you can do this off the big terminal on the starter relay, that way the fusible link remains as a fail safe in case of a big short someplace. I would also suggest a circuit breaker, appropriately sized, on the load side of both relays as added protection. I like to start this conversion with a new light switch and a new dimmer switch so I know I have good connections. You will also want to check the ground connection from the headlights to the core support and all headlight plugs for corrosion. Install new plugs as necessary.
Finally, a lot of these C-Bodies have settled down some at the rear end as the rear springs have aged. This in turn will cause the headlights to be aimed too high which provides poor lighting to the street surface where it is needed, check the aim on your lights before doing anything else. Also check the operating voltage of the charging circuit to be sure you have adequate voltage to properly energize the lighting circuit for good bright lights.
Dave
