71 LA 340 timings moved!! how?? looking for help

Normal slippage is for the timing to retard, not advance. So that makes me think distributor....

Maybe the wiring from the pickup in the distributor got reversed in the electrical fixes. If it was backwards to start with, then the ignition would trigger on the back edge of the trigger pulse, and you would have to advance the cam to get timing to a normal position. Then if this reversed wiring was corrected, now the ignition is firing off of the front edge of the trigger pulse (which is the correct edge) and the timing is considerably advanced.

The other thing is the damper ring slipping as mentioned; it will slip backwards and make the timing look advanced. But that would not make the car un any differently.

And the vacuum advance rod could be jammed up, keeping things far advanced.