2 batteries
I don't see any reason to run two batteries in these cars. Nowadays you can buy INCREDIBLY powerful auto batteries, most of which are overkill with most street engines
What engine combo, HP are you running?
AND it's "not the battery" that is needed to run big stereos, fans, etc, it's a larger alternator, and you do NOT want to try that with factory wiring, the factory bulkhead connector, and the factory ammeter
Please READ this article, which details a few of the problems:
Generally,
not a large enough alternator, nor do the factory originals put out enough at lower rpm
not large enough wiring
the bulkhead connector was NEVER designed to carry much amperage
the factory ammeter has it's own problems
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
which came from here:
http://www.madelectrical.com/electrical-tech.shtml