[Mike Taylor 3601]

I would guess that since you had wear problems before, you need to check how cam/dist gear are meshing and check teeth on cam first. If cam gear teeth are sharp from wear you'll have to replace cam because it will eat every dist. gear you put on it.
Most likely you're gears are too tight or loose ( backlash) or gear on cam is worn and eating dist. gears.
Mike Taylor 3601