Hesitation at 60 mph and up

The advice is good but in my experience, when the engine begins to starve for fuel from a restriction somewhere, you can actually make it worse by giving it some heavy foot.

I don't advocate trying to drive faster to try this, but when you have a good clear road, stop and take off and run it up to the speed limit pretty hard. If it takes off and goes it's probably not a restriction.

If it loses power the more you try to force it to go, then that's a restriction. The carb bowl will run dry faster than the fuel pump can supply it, so then the engine begins to sputter and lose power. Once you let up on the pedal, the fuel pump can catch up and it runs again.

My feeling is that there's dirt in the carb and it needs to be overhauled by someone who is competent. If you find dirt and rust somewhere then that issue won't go away until the tank gets cleaned or replaced.