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

Take a permanent maker and draw a line across the balancer, reset timing to 12 initial for now, tighten distributor and drive it.
Check balancer to see if line is straight across or if it shifted from the center, ring slip.

A distributor with mechanical advane will have some movement , depending on how light the springs are, large the bushing or slot is will determine how much.
It's also possible to reverse the polarity on the pick up wires, and end up changing the timing by a lot.

Key here is...did the idle rpm ever change from what it was before? or was it just performance that went away?.....32 idle would have it well above 1000 rpm at idle.