340 Stalling Hot???

OK, I've got a 340 in a '68 Cuda, Mopar electronic dist, orange box, mild cam, timing is fine, vac. is fine, don't know what my fuel pressure is, but its a stock fuel pump, and fuel lines are in the factory locations. The car starts and runs great from a cold start all they way up to about an hour and a half of driving. Once everything gets hot (under the hood), temp running at 190*, she starts to stumble sitting at a light, then stalls as I start give it throttle pulling away from a light, then extreamly hard starting, pumping the gas to get it going, and almost have to neutral drop it to keep her running. I did install the Edlebrock black spacer plate (3/4") under my Edlebrock 1406 carb last year thinking it was a fuel boil situation, and thought I had it licked, but I guess I never drove it long enough in the hot weather for it to happen. I'm looking for any suggesions, I can't really tell if its fuel or spark, but I'm thinking its fuel because I have to pump the crap out of the gas to get her started again. I was thinking to replace the orange box with the chrome one, but don't want to just throw money at it. Let me know what you guys think.