1991 Isuzu Truck Intermittent stalling

The truck recently had a new Weber carburetor installed and that has taken care of the hard cold starting problems. The aggravating thing is an intermittent stalling problem. The truck has a good battery, new plugs wires and rotor. The scenario goes like this: I will go for an errand like the grocery store. No problem on the trip to the store. After I have been there for maybe twenty minutes, the truck starts up fine and accelerates normally for about half a block then begins it's stall and I look for a place to pull over. I can pretty much start it up again immediately and it will run just fine the rest of the way home. It doesn't do it predictably enough for the mechanics to diagnose it. The truck has a little oil leak around the distributor, which I am planning to repair, if I can feel that the truck is reliable enough to keep. Any ideas would be greatly appreciated.