FWIW, I like the Holley 2210-family 2bbl. More refined and efficient than the Stromberg WWC and Carter BBD that it replaced. It does have the same issues with the air horn raising in the center due to over-tightening of the air cleaner wing nut as the Strombergs did. The BBDs had their air cleaner stud attached to a heavy wire which attached to the sides of the air cleaner mounting area. But when the air horn deforms, it breaches the float bowl's rear wall and where it seals against the air horn, allowing raw fuel to be pulled into the venturi area when the choke valve closes. One tip-off that this has happened is when the choke valve hangs on the air horn, adjacent to the air cleaner stud. BUT Chrysler put out a TSB and "Bridge Kit" to fix it in 1972. And it worked well as I did that on our '72 Newport 400 2bbl. BTAIM
When it dies after being run for a while, that's when the inductive timing light can be handy to have nearby, plus a long flat-blade screwdriver to short across the starter relay with the key in "run". Not specifically to check the spark timing, just to check for sparks happening.
Problem is that "spark" and "fuel" issues can tend to act the same in some situations. Making it difficult to diagnose correctly.
I have a '68 Buick LeSabre 350. After I got it, I did the normal tune-up stuff to establish a baseline of sorts with it. Plugs, points, wires, etc. One day I had it running and it started to lose rpm. I quickly went to the driver's seat and started pumping the accel pedal and it came back. No real rhyme or reason, but it happened unexpectedly, otherwise running fine. It would do it running down the road, too. The last time it happened I was taking it to my shadetree shop for storage. On the way there, it started dieing out. I'd coast to the shoulder of the access road, put it in "N" and try to start it by pumping the accel pedal quickly until it would catch, then I'd quickly pop it into "D" (one wheel on the dirt) and seek to continue to the shop. That night, it happened a few times, but we finally got there and parked it inside. I got a new fuel pump for it, for good measure.
One night, I decided to replace the fuel pump, just to know that it had been done. When I started it that night, it sounded better than it ever had since I'd owned it. Problem solved. Obviously, the existing pump had some issue with the valves in it where they would get into a particular position and leak internally between themselves (or something like that). I remembered a late uncle who had a similar situation on his '60 LeSabre. Back when you could rebuild fuel pumps! It was the valves in that pump having issues, too.
Then, the issue of fuel pump pushrod wear has come up in this forum a good bit lately, too. Something not usually worried about.
In one respect, it might be ignition as you can get it to start with greatly-advanced timing. Which is where the timing light checks can come in. On the other hand, it could be a fuel issue.
The fuel pump might be recent, but even with ethanol-resistant diaphrams, allegedly, if the pump is allowed to dry out from non-driving/running, that "resistant" diaphram can allegedly become brittle and have durability issues. But the pump can oily pump so much with a worn fuel pump pushrod (think "decreased lift on the cam lobe" sort of thing, resulting in lower volumes pumped). Maybe a little bit of both?
Please keep us posted on your diagnostics,
CBODY67
