won't start when hot

[Ronnny]

My 68 long bed has a 350 with a 400 tranny. It has the points from the first motor it had. The truck starts and runs fine. If you cut the motor off it will start right back up. But if you turn it off long enough to get gas or run into a store it will not restart. It does run good. i was told maybe the coil but have not swapped it out yet to see. I plan on putting in a hei dist. soon. the carb runs fine and i do not think it is the choke but could be wrong. If i cut it off i can start right back up. But if i let it set 5 minutes it needs to go ahead and set a another 10 or so. any other ideas?