My first thought was fuel and the second ignition. You can't rule out fuel pressure unless you have a pressure gauge . Does it have a fuel pressure gauge? My 67 Coronet street car was running out of fuel and to diagnose it I temporarily tied a fuel pressure gauge to the wiper - it told me that my pressure was dropping to near zero on acceleration - was temperature dependant.
You could have an ignition box, pickup or ignition coil failing when it gets hot.
The above are my initial thoughts too.
Coil, distributor pickup, fuel delivery problem when hot, etc.
