Headlight volts drop

[Mustang]

i notice when I switch my lights on sometimes the clocks go off then come back on, also if I pull the pass light switch in. I did a test with the lights disconnected and that stopped the clocks going out. I’ve checked the battery voltage and it drops quite a bit when the lights go on, I guess it’s enough to cut the clocks out. Has anyone altered their lights to fire them off a relay? Would it make any difference? Gen 1 2001