There are a few things that will cause a bog on acceleration, and other issues that will cause somewhat related performance issues. If the hesitation is occurring only when the engine has been running a while, and not when it is warming up or recently warmed up, it is possible you are getting some impact from vapor lock - - but not likely as vapor lock tends to cause a more total kind of fuel starvation, not just on acceleration. A weak fuel pump will reduce the volume of fuel being sent into the carburetor fuel bowl, and often will send liquid fuel outside the fuel pump housing, or worse yet, send liquid gasoline into the crankcase 0 which has a horrible impact on the ability of engine oil tp protect the lubricated parts of the engine. It sounds like you are already clued in on the fuel pump side effects - which is good to know. It is possible a low pump pressure or volume (or both) can cause the fuel level inside the fuel bowl to be too low, which will certainly cause a hesitation.
Some other causes include a problem with the accelerator pump system of the carburetor, as mentioned by Mike Jones. Another cause could be someone rebuilt the card or made internal changes to lower the fuel level setting with the fuel bowl float in an effort to increase fuel economy (this was done to our 1973 Mustang 302 2v, causing a slight off idle hesitation. I corrected it when I rebuilt the carb. Other things were also done wrong. Video at the link below, if interested). In some of the video descriptions I include time markers where certain items are discussed, so if you do not feel like watching the entire video you can just Fast Forward to those areas in the video.
https://youtu.be/U-ETjhRqUwQ
An intake manifold leak can contribute to an excessively lean condition that can interfere with the effectiveness of an accelerator pump on acceleration. Another cause is a ruptured or leaking distributor vacuum advance diaphragm, or ported vacuum not making it to the vacuum advance diaphragm. If the ignition timing is not set correctly it can cause a hesitation. Yet another possible cause is an EGR Valve that is opening a little too much or too soon (or both), but I see no evidence of an EGR valve on your Edelbrock intake manifold - so you can rule that out.
One of the things I check for with hesitation problems is if it happens with a cold engine as well as well as when the engine is up to normal temperature. If it occurs mostly at lower RPMs with the throttle being opened, but less noticeable at high speeds where the engine is already running at 2,000 RPM, the problem is most likely related to the carburetor.
In the following links I show how various vacuum systems work, to include showing how to test a distributor Vacuum Advance Diaphragm for leakage. There is a lot of info in these videos, and some overlapping information. Dorry for the overlapping, but once you have learned how these systems work, and how to test them, you will understand far more about your engine and how it is controlled and affected by the various vacuum systems.
https://youtu.be/DtBcK7Lxq1Q
https://youtu.be/sLwXlsHBd4k
https://youtu.be/ohw1oRlcC4c
