Hotrodwagon,

A bunch of years ago I had a very similar problem with a 46 Delivery I had. It would randomly quit once it was warmed up. I chased the problem for quite a while, messing with the fuel system mostly because it acted like it was running out of gas. Finally figured out that it was the stock 46 ignition switch thanks to an old time mechanic I happened to mention it to. Seems that the switch was weak and would slowly heat up and then lose contact. Replaced the switch and never had another problem.

Just another thing to check, if you're still running the stock switch.