Something doesn't sound right with the headlamp door action tied to the instrument illumination rheostat. There must be something cross wired in there. I would get that right before replacing anything. Specifically check the switch wiring to this diagram:
http://www.panteraplace.com/El...0SWITCH%20WIRING.pdf
Here is the best wiring diagram reference site.
http://www.panteraplace.com/page107.htm
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