The big problem with an 8 volt battery is the necessity to adjust the regulator output to 9.5 volts to keep it charged. That's rough on points, lights, and possibly the gas gauge. It's really impractical to put enough voltage-dropping stuff in place to get the extra voltage only to the starter. We used to deal with the same thing back in the mid-50's at Dad's shop when there were a lot of 6V cars on the road, and a local battery maker started selling their version of an 8V setup.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!