We replaced the carbs with a new set of Spanish-made Webers. The carbs were fully set up as we all know they must be. We used the re-jetting and float setup recommendations of https://www.wayoutwestie.com/m...he-whole-of-england/.
We left the faulty fuel pressure gauge and fuel regulator on but set the fuel pressure independently with an accurate pressure gauge. Those parts will be replaced next. The carbs are running beautifully.
I was going to sell the old EMPI carbs on Craig's List or Ebay but they are junk. It's a miracle that I didn't burn up the car in trying to get to the bottom of the issue.
Thanks to everyone who provided useful help on this.