Ok, fuel pressure gauge arrived this week and I finally had a moment to install it temporarily so I could see the fuel pressure during a stall. Seems to be holding perfectly steady at 4.5 PSI. I made a quick video showing the pressure as it stalls:
https://youtu.be/lvZox3oGsLQ
Doing some quick research, it looks like 4.5 to 6 PSI is normal for the L6 with a Rochester Monojet, so I think we can finally rule out fuel pressure as an issue.
Moving on the pressure testing the carb, I guess.