Regarding your puzzler: Just a thought that occurs to me from an experience I had 45 years ago with a '72 Corvette LT-1:
I had the carburetor rebuilt and messed with several times by various mechanics over a year-long period because every time I would pull out to pass somebody on a two-lane, the car would absolutely stall like I had turned off the key. Sure looked like a jerk to the drivers of the cars I would try to pass. I would slow back down to maybe 25 mph, and the car would revive and run like nothing ever happened - at least until I punched it again.
Everybody figured it had to be a clogged fuel line or dirt in the jets or something like that. So we kept looking at fuel supply for the problem. But finally someone suggested we try replacing the coil because they can give some similarly odd symptoms when they fail. We put in a new coil and the car never cut out like that again. As Mr. Ripley pointed out yesterday - ninety percent of carburetor problems are electrical.
It's such a simple thing to try in case you haven't already..........................
Keith Boonstra