I do love the simplicity and quiet of a mechanical pump. I installed a Carter m6903 on my C body driver (440, 474 purple shaft, manifolds). It might run 15s or 16s on a good day, but to be honest I have not actually tried it. Just an old family sized car with a big motor for fun. I've got a plastic spacer under the carb and it hasn't given me any trouble as of yet, but if it acts up I'd probably first try a return line before doing anything drastic. I've had pretty good luck with return systems in the past keeping the fuel cool...