headlights are not working . ground issue ? 1973 dart slant 6

Ok . I put an alligator clip lead , one end on the ground blade of the driver side HL ( still connected ) . I put the other clip on the bumper and both of the headlights came on . They are working properly . High beams come on .

I would like to try to find and fix the bad ground if its possible . I just don't know how to do that . Any suggestions ? Also , i don't know if its related because the previous owner messed with some things , but , it appears that none of the dash cluster lights come on . i will double check this when night comes . Definitely no high beam light and definitely no turn signal lights . He bypassed the ammeter . The temp and fuel gauges operate , but unknown if accurate . I will start with changing bulbs , but doubt all of them blew out .
You're simply going to have to do some manual back tracing of the ground blade in the headlight connector. Find the wire color on the ground blade connector and trace it back through the harness until you find where it attaches to ground.