Won't start when hot!

[chevy72pu]

Ok, so the rebuilt 350 runs like a top, no overheating, no leaks. All is well till I shut it off after more than 7-8 miles of driving. It will not restart until it sits for 30 mins or so. The battery turns her over fine when she is cold, but can't manage to do so when the engine is hot. Swapped the battery out of Lil' Red and the same thing happened. We put double hump heads on the 350, so I'm wondering, do I need a new stronger battery or a high torque starter? BTW it will crank with a jump start even when it is hot. I had Advance Auto Parts check it and the print out showed a 25 amp drop on the battery and the alternator is fine at idle.