MSD Pro Billet ignition- are these unusually "voltage sensitive?" Got stranded, looking for ideas

I had a Optima red battery fail on me.....going down a hill!! Engine just died. No brakes or steering. Yikes! When I got it stopped, I measured the voltage & it was about 6-8; left it for a few hours & the voltage recovered but not fully. I believe an internal short in the battery. Under warranty still, Optima would not replace it. Had to sue the bastards to get the money. Preparing for this, I found lots of examples on the net of failed Op batteries.
Try a new battery first, you might have a different problem.