LA360 initial timing too high - are there different timing covers?

To check the pick-up polarity, wouldn't it be easier to just swap the wires connections with short wire jumpers?

FWIW, the pickup polarity being reversed would not change the timing on the damper, just the position of the distributor to get the timing set right. So by itself, it would not cause the timing set to need to be 50 degrees advanced. BUT it really WOULD effect the rotor phasing. So that is a good thought.

Checking the mechanical advance is a good idea. It might gives some clues.

Just a dumb question for the OP: You are putting the timing light pickup clamp on the spark wire to the #1 cylinder right? Just looking for anything clue.