out of gas?

[zone78]

i own a 69 mach 1 428cj w/4 speed.
the problem i have after the car is fully warmed up (sometimes 10 min or as long as 40 min) the car will act like it is out of gas.
The car will generally start back up after 3 or 4 turnovers and may travel anywhere from 100 feet to a mile before "ruuning out of gas" again.
I have replaced the filter on the sending unit in gas tank, the fuel line from gas tank, 2 new fuel pumps,and have had the carb professionally rebuilt,eacvh of these with no success. I have able to duplicate this in my garage and have seen the car run right out of gas at approx 2500 rpm. any help would be appreciated. thanks ken