Mystery solved... maybe

Maybe the fuel tank outlet screen is collapsing shut?

If the tank cap was not venting the tank would have a concave dent to it and when the cap is opened you would hear the tank quickly fill with air a ....pop or whooshing sound. I would investigate a fuel restriction because as you said , a few  minutes and it starts and runs so IMHO  a hose/filter/ tank screen/ line ....something is getting clogged.  

Not questioning Alan's advice, but something else occurs to me, especially since you say you couldn't hear the fuel pump at one point.

Now is the season for iffy electrical contacts to get more iffy. Have you checked all the connections to the fuel pump for corrosion, including ground?

Was it damp or wet at Carlisle?

"Was it damp or wet at Carlisle?"

BWAAAHAAAHAAA, now that is funny . . .

Actually no, when I had the stalling episodes it wasn't damp, nor was it yesterday (upper 70s and sunny - in DECEMBER?!).  It usually happens (IIRC) within the first 1/4 of a tank after a refill, which was another reason I considered a venting issue.  I guess I need to let the gas get low and see if I can see anything going on in the tank.

Possibility of vapor lock?  

As Alan and Bill mentioned, it sounds like the screen at the bottom of the tank is plugged. Drain the tank, disconnect the fitting/fuel line at the bottom and there should be a screen. It's there to keep the bigger chunks from reaching the fuel pump and carburetor(s). With the motion of fuel flowing through, it could be getting plugged with rust and whatever else is in there.

i did that on my last VW and it was plugged with gunky greasy stuff.

POS fuel pump?

I'm in on the varnish gunk at bottom of tank!  Gets stirred up when you refill tank. Ethanol attracts moisture and cleans any gunk in tank which gets suspended and sucked to filter sock or gas intake.  Tends to dissolve older rubber fuel lines.  

It's the same fuel pump that Danny runs in his car.  I replaced the Hucho (sp?) that I'd had for years when I was chasing down the carb gremlin last fall.  I feel confident that it isn't the pump as I've had it occur with both.  As for bad fuels, I always use ethanol free here at home, but can't always get it on the road.  The last tank with any ethanol was on the way back from Carlisle.

Lane said-

" It usually happens (IIRC) within the first 1/4 of a tank after a refill"

"I feel confident that it isn't the pump as I've had it occur with both"

Greg said- 

"I'm in on the varnish gunk at bottom of tank!  Gets stirred up when you refill tank..."

Drain the tank, take the fuel line fitting off, pull the screen. You'll be surprised at all the crap that comes out. Clean it out, put it back together. Problem solved.

"Drain the tank" -- so easy to say.  I wonder if there is any way to inspect the innards, and actually see if the outlet is blocked on the inside.  I recall reading in a Haynes manual once upon a time about doing a gas tank inspection, their advice was, "Using a torch, inspect the inside of the tank . . ."  Of course, one would have to understand that in British, "torch" means flashlight.

LMAO as I write this a I can just hear Lane say: " Hold My Beer I Got This" .

Lighting the ole British torch so to speak for a look n see into the bowels of the petrol tank, suddenly there goes Lane across the garage passing the missing brass carb thingy as his newly installed "innards" mesh comes unraveled.....

I've had the vent line kink when loading to much stuff in the trunk. I would check the routing of the hose and a warm day can soften the hose enough to kink it at times, it doesn't have to be closed off completely to starve dual carbs.

Was it a warm day when you drove back from Carlisle?. The lower fuel level as you indicated above will allow for more fuel vapor and put more demand on that vent line.

Mike - Yes, it was pretty warm on the Carlisle trip this year.  Hmmm...

Hold my beer.  I got this!

Once the tank has been drained, and the mesh inlet cleaned, change your fuel filters, just to be safe....   How do he know????