Clunk could be the starter solenoid or the spring in the dog gear.
Do you have a multimeter to confirm the alternator is charging the battery?

When you say it won't go, is it turning over at all? Or is it turning over slowly, or is it turning g over but not starting.

Next check all your grounds, expecially the cables to the starter. These can corrode internally as well. You can Bench test the starter to see if it operates normally with good connections