My middle brother has a 1973 Dodge Challenger. Well he got in an incident a mile from where he brought the car. We limped the car home. After the car was repaired we started having starting issues. So we put on new battery cables, ignition box, and starter. Well the headlights and radio work (so we got power). But when you try to start the car it just clicks ? It doesn't even turn over !

since you replaced the cables, that should take care of dirty connections. make sure they are correct, and tight. make sure the battery has a good charge. after that, might be a bad starter or relay.

Where is the starter relays at on a E body ?

If its clicking the relay is getting power and working. Sounds like the starter cables connections or a stuck starter.

What condition is the battery in?
What kind of "incident" occurred?

on the starter itself with a screwdriver jump from the large(batt) terminal to the small (solenoid) terminal. Be careful not to touch the screwdriver to the starter body. If it cranks the starter is obviously good so go up to the relay & with the screwdriver jump from the large (batt) terminal to the fairly large brown WIRE that goes down to the starter. If it cranks plug the brown wire back onto its terminal & take off the neutral safety switch WIRE on the starter relay & ID it as it is plugged on a male terminal that says "grn" on the brown face of the neutral safety switch & ground the male TERMINAL on the relay with a jumper wire to GROUND & see if it cranks with the ign key.

Thanks gunna try that tomorrow