Fuel pump, vapor lock? My truck died on the hi-way.

[AirSpeed]

Yesterday after a long three days of new car shopping I was headed home, about an 80 mile trip and my 72 GMC started cutting out and finally died on the side of the road. It's a 72 4X4 with 350/350. It was a hot day, about 106, truck was running cool but suddenly would run out of fuel and die. The fuel filter was empty, no gas. After a while I tried to start it and it fired right up, ran fine. I had a tow truck on the way so I decided to take the tow home just in case it happened again. When we took the truck of the tow truck I could smell gas really bad in the cab, I occasionally got a wiff of gas in the past but this was like someone dumped a cup of gas in there. I let it air out and the truck started right up, there was no gas on the bed of the tow truck or anywhere in the cab that I could find , nothing dripping under the truck, I'm at a loss. Any ideas what and where I should start looking?