LA small block timing is suddenly way off

I have an inline fuel filter -> mechanical fuel pump -> inline Edelbrock fuel filter -> inline fuel pressure gauge -> line then splits and feeds dual Edelbrock 1404 carbs. No fuel pressure regulator. I have a steady 5psi of fuel pressure on the gauge at idle and at least up to around 2,000 rpms. 5psi used to work OK, but maybe 5psi is generally too high? I probably should install an inline fuel pressure regulator but have not researched what a good psi setting would be. Since I have a steady 5psi of fuel pressure I believe my fuel filters are not clogged. I also peered inside the fuel inlet of the carbs and down inside the carbs, pulled out metering rods, I don't see any gummed up carb parts yet. Have not pulled the tops of the carbs of yet to check floats.

I'm also thinking maybe I should buy a new MSD 6AL ignition box in case mine went bad. This bad missing problem was somewhat intermittent for the last few drives before it became permanent. I could try the ignition isolation test (pull one spark plug wire at a time) but right now there is so much missing going on I don't think I could tell anything. As you can tell I'm still trying to narrow down the real problem.