Could be the solinoid on the starter. There should be a wire form the solinoid that shoots a straight 12 volts to the coil for hot starts. The hot wire from the switch to the coil will be cut back to about 6 volts when the truck is hot enought to run it but makes for hard starting hot. Try hooking a jumper wire form the batery to the plus side of the coil on a hot start and see if that helps. Doing this bypasses the switch so be careful.
