Bjorn has a good point, your starter could be getting hot from your headers. Good news is as long as the header does not touch the starter you should be ok.

Lemme,
It looks like your battery is rated at 500 cranking amps.
Your better off with a 900 or more cranking amp battery.
Your engine is very tight. Make sure you have good cooling fan.
I remember push starting my coupe at the gas station after filling up. Engine just heated up big time and tight as hell. It would barely turn over.