Hey, I got it fixed, status report:
RickD, you were right, problem was steel on steel. The old steel line just would not conform with the old steel fitting. I called around a bit. Speed shop only had "repair" units, for if the carb was stripped out. Suggested a carb shop, that was a dead end, the guy was clueless. So I called a chevy dealer, the parts man knew the part, found a # for it, but said no it is longer made. He suggested a place, Speedometer Electric, turns out they also do carbs. The fellow there got me a new fitting. Brass, not steel. It looks a bit different, but functionally identical. I popped that puppy on, followed his suggestion to put some grease on the threads and flare (to prevent galling). Only problem was the new unit was a bit deeper, the fuel filter needed to be about 1/8" longer. I made up a gasket to space it out OK, no biggie. Tightened it up "reasonably" tight, not super tight, just what felt should be right. Fired it up, not a drop of leakage. Yay!
I didn't want to use teflon tape, as the flare is supposed to seal on the fitting, if fuel gets to the threads then something is wrong.
I'm so happy, the new quadrajet (which I spent 3 days rebuilding) runs perfectly!
Thanks everyone for your ideas and support!
now: '73 LT; '79 Z28
then: '67 coupe; '88 IROC; '95 Z28