305 surging at Highway speed only

[tutone]

Hey all. I chuckle at some of the threads that have obvious answers to, but I think I am troubleshooting one for myself that has me scratching my head.
Truck-- org 6 cyl
Org tank and 5/16 gas line to pump
(I have a new sender-3/8) not installed
Installed a 305/700r4
I have driven it 500-600 miles, mostly around the house, 40-50 mph and it funs like a champ. Trans is adj properly, I unscrewed the gas cap while it was acting up, no change.
At 55 plus it acts like the thing is starving for fuel but only at that speed or faster. It will run then fall flat on its face, then pick back up and do it again.
Pull off the road and let it idle a minute, your good for a mile or two then all over again.
Plan is to change the sender, fuel line, and fuel filter.
Any more ideas or anyone have a similar problem that they solved.?