Dragon,
I agree with the comment on air flow through the radiator. When I had my Lone Star I purchased a really neat shroud and fan combo from Vintage Air that fit the LSC radiator, had the little trap doors and the fan pulled 2900 CFM if my memory serves me right. That in combination with some shrouding around the outside of the radiator to force all the air through the radiator cured any heating issues I had. Even in 100 plus degree days that we have here in Texas, the car ran at 190 - 195.
Here's a photo that shows it:
