360 motor loses ignition when warm

I had the motor fired up yesterday idling, then bringing the rpms up and down, repeating for about twenty minutes which brought the motor temp up to 200 degrees which is warm for this motor when I'm driving it. I shut it off and started it up at least ten times with no issues whatsoever. Started up immediately every time like it was cold..figured for the $100-$130 bucks to replace the coil, ballast and ignition to give me a little peace of mind was worth it. What else could it be? Distributor?