When blinkers are on gauge moves up and down with the blinker, about 1/8 tank each way, also when the headlights come on, the gauge drops 1/4 tank. Had the sender out and it tested to spec. Cleaned all connections at sender, and it did not get any better. Any Ideas?

 

Possibly a loose or bad ground at the cluster.

 

X2 sounds like a bad ground somewhere. Has there been a repair (cut and splice) on the gas line. I'm not familiar with your model car but some models are grounded through the gas line or it is just back feeding from a bad ground in the turn signal or lights....Tedd

 

Common problem on 63-64. Check grounds on the instrument cluster. All of mine do it and it's just not been enough of a priority to disassemble the dash and pull the cluster, though it's not really a bad job.