[Sloan66]

I would appreciate any advise.
I have a 307 2 bl Truck runs good at speed, but at slow speeds "bucks" under accelration. I have checked all fuel connections, changed filter, cleaned carb 3x, changed accelerator pump, verified timing, adjusted air/fuel mixture, pulled plugs. It seems to be a fuel issue as vehicle idles fine, sustains speed, the bucking only occurs under accelration , most noticable in 2nd and 3rd gear. Could it be bad fuel pump?