Tom,
First allow me to welcome you to the DeTomaso Community and Forums. We are very glad to have you with us.
Regarding your lighting problem:
You'll find schematics for the wiring system on Mike Daley's sight,
http://www.thepanteraplace.comYou'll need a volt meter or a test light. With the car running, the ignition key in the proper position, etc, follow the circuit and start checking for voltage. Do not start at the beginning or end of the circuit, start somewhere in the middle. If you find voltage in the middle, move forward towards the "load" (device being energized, in this case the lights). If you don't find voltage in the middle, then move backwards towards the source (a switch, a fuse, etc). The idea is to find where the voltage is interrupted. IF you find voltage all the way to the "load" (in this case the lights) but the lights are still not working, then its a ground problem.
Another way to identify a ground problem, there will be voltage on both sides of the load if it is ungrounded. To illustrate, both wires leadng to the inoperative lamp will have voltage if it is a ground problem.
take care.