Some years ago while traveling from Long Island to Florida via Asheville, NC, I had a voltage regulator go intermittent, difficult to diagnose as it would indicate charging well when tested until I was fortunate one time to see it kick in and out a few times. Fuel filter could be old and clogged as already mentioned. Next time when it sputters to a stop, open the gas cap and listen for suction, I've had the fuel tank vent clog in the past, once the negative pressure in the tank increases enough, fuel will not flow to the carbs.