Just to contribute, I just changed out a 5 yr old stocker type Carter pump for a Carter Super Street. I’m currently running a 326 and had some issues, mainly heat soak/vapor lock, I believe. If I was at a stop light for a minute or two, and then took off full throttle, a couple seconds after I shifted into 3rd it would fall on its face. Same thing when I took it to the strip for the first time last summer.
I have a gauge on the inlet of my Qjet, at idle it would bounce between 5-7 psi. With the new pump it is almost rock solid at just under 6. Unfortunately I still have 5/16” fuel lines, I replaced em when I first built the car, before I knew better
Figured I’d chime in and say that even a 326 showed some improvement with a better pump.