340 Stalling Hot???

I just went through the same exact thing. If you have a fuel pressure gauge or a clear fuel filter(so you can see if it not getting fuel) it will help you find out if the problem is fuel related. I would loose pressure and also my filter would slowly go dry AFTER the motor got hot.... ran perfect until it got hot. The car stalled on me a few times so I started looking to find the problem. I cranked the car up and let it idle until something happened... sure enough it happened. The first thing that happened was my fuel pressure started to fall then bubbles started to pop up from the fuel pump side in the clear filter. Then the fuel pressure fell to 4 psi and then motor started going lean. What I found was my fuel line was not ran properly and was causing vapor lock situation.