"bucking" at high power settings

[Nigel70]

My 70 S2A is bucking at high power settings. e.g. 45-50 MPH especially going uphill until I let off the gas until it begins running smoothly. I have inspected the filter screen at the carburetor and it is clear. The see through in line gas filter is full and appears clean.
Could my problem be because the mechanical fuel pump can't keep up? FYI, I have an in line electric fuel pump mounted before the mechanical pump. Any ideas??

[Snowboy71]

I had similar issues that were resolved by replacing the points and condenser. The ones I replaced were not that old but somehow new ones did the trick and it was a cheap fix.

[erik88lr]

I installed a small pressure gauge at the carb inlet and it showed the pressure dropping to zero under high load/high RPM conditions. After trying multiple new mechanical pumps and checking for blockages an electric pump mounted in parallel corrected the problem. It's switched and only comes on when I flick the switch upon noticing the truck start to buck due to fuel starvation.