['76 Big Block]

I noticed (from your photos) that you have what looks to be a brand bew Edelbrock carburetor, but didn't see anywhere in your threads that the float levels have been checked and verified.
I also didn't see if you were having the problem during hard acceleration, or just cruising along.
Since you've replaced pump and filter, I would start looking at carb issues----even new ones can be defective/improperly adjusted.
I experienced the same symptom on my big block, I replaced fuel pumps and filters several times before digging deeper and finding my issue was the shredded sock filter in the tank. It would run fine after sitting, but starve when accelerating or just cruising.
Since you've eliminated the sock filters, I'd look at the carb.
Good Luck!