I recently purchased a very sweet 72 gto.I have noticed when I turn on the headlamps then step on the brakes or use the turn signals the engine will shut down like you turned off the ignition switch,also the headlamps will dim with the turn signals.the tach also flickers.The car has new battery and alternator,but I'm wondering about the grounding the only ground I can see is from battery to block.  

Got this fixed simply by adding a ground cable from block to frame and block to firewall.no cutting out now and the lights are brighter.hope this helps someone else that may be fighting a similar problem.