I have a 1989 F-150 XLT I just picked up and the front fuel tank works fine at idle while sitting level but once I drive it up a hill it chugs out and I have to switch to the rear tank to keep going. Looking for the best fix I already changed a filter and a pump but still won’t work. What my best options to fix it or rig it differently.

 

First,,,which pump did you change?

Good possibility there is a problem with the pick up tube in the tank giving you trouble.
The only thing that usually changes when going up hill is the angle of the fuel inside the tank.

 

I have change the in tank pump in front tank and is there a way to test this or fix it. If it’s the pick up

 

The only way to know is to remove the pump assy and look it over carefully for any holes or cracks on the pick up tube.

Did you change only the pump motor or the entire assy ? (Entire assy called fuel pump module)

What happens if you have a full tank and go up hill?

Is there any way you can check the fuel pressure of both pumps ? You say you replaced the pump in that tank, right ? The better thing to do is verify fuel pressure.
Were any checks done to make sure full power is getting to that fuel pump? Does the engine RPM go up when you raise fuel demand while vehicle is level?