I have also had a number of Optima Red tops go bad on me. They do not hold up well on a non daily driver, unless you put a battery tender on there. Yellow tops can handle not being run, better. Currently I am making the switch to Odyssey.
I also run duel Flex-a-Lites, but mine run on a thermostat and I've never had any problems.
On the alternator, I see this on the Pantera Wiki:
"It is a plain-vanilla Ford Motorcraft alternator for a '72 Ford. You may find a 47-amp, a 63-amp or 75 or100-amp 'Police Specials'- they all use the same cases and are visually identical. To find a high output unit, I had to take a couple of junkyard refugees to an auto-electric shop and let then spin them up on their tester to see which was which. IMHO, the 47- & 63-amp are too low output to support headlights, AC, a stereo, two radiator fans and a CB, at low rpm in traffic. Cheers- J Deryke"