Hi Marty,
Great question, this is one that is commonly asked, and you will get various opinions on the subject. Here is mine:
I would use a quality dextron III or Mopar's ATF+3 in your transmission. I would recommend frequent fluid and filter changes, and even more so if you are bracket racing your car or using a higher than stock stall speed with street driving. Fluid breaks down with heat, and loses its ability to clean, lubricate and cool the transmission.
I would stay away from Type F fluid, as it breaks down very fast with heat in my opinion.
Some of my customers like to use a synthetic based fluid, such as red line. I personally have not seen any ill effects from using this type of fluid if it is within your budget. Some transmission builders will tell you to stay away from synthetic fluid. I still recommend frequent fluid and filter changes with this fluid.
I use ATF+4 in my cars, which is Chrysler's newest transmission fluid specified for all 98 and up Chrysler products. It is highly recommended to use this fluid with a lock up torque converter application. This fluid has additional additives to resist heat, foaming and corrosion.
Chris