I can either adjust my throttle cable so that when the pedal is floored I get WOT but it won't return to idle, or I adjust it for idle and I can only go 80% throttle when the pedal is fully pressed.

Any solutions?

Carburetor is a 4160

 

I think I solved my own problem. If I move my throttle linkage lower on the throttle arm I can get another 1" of travel.

 

Love them old trucks....
Keep us posted.....