[vettestr]

You hae been gien great adise already but a couple of steps farther may help your case. Check to see if your regulator output is set properly when at operating temp. Voltage should be a min of 14.2 volts. so alt and reg can each be checked. An inductive meter used to check starter amp dram can be used to check total current demand on the battery and the charging system.
A couple of tricks needed on one of my cars was to run 2 batteries for that demand under the highest conditions. The injection ECM did not like power sages nor doesa MSD ignition controler. I was running multiple fans and electric fuel pumps and a coolant xfer pump etc...
My local alt and starter rebuild shop hot rodded my alt. with an internal modification and also swaped the pulley to increase rpm of the alt at low engine RPM. Ask your local alternator rebuilder to HOT ROD for a higher amp output potential and make it available at low engine RPM. I also hate the underdrive engine pulley kits because they can cause all kinds of trouble. good luck and enjoy.