Too much timing???

Just a long shot: With this being heat sensitive, it could well be electrical. Do you have the correct ballast and coil? Or is this triggering a different ignition module? If so, what?

Here are the instructions: make sure it is wired this way....an inverted trigger line (green and brown reversed) to another ignition module will make the timing erratic or move around.
[ame]http://documents.holley.com/mallory_instructions_unilite_distributor_37_38_45_47.pdf[/ame]

BTW, do you have a voltmeter in the car? If so, what is the reading cold versus hot, and idle versus 3500 RPM?