Caster angle plays a crucial role in returning the wheels to center - especially on bumpy roads. That's why bicycles are so stable with on;y one front wheel.

Either the steering box is messed up or there is a big problem with the caster angle on your front end.

I can drive at any speed on smooth and bumpy roads and the truck tracks straight. Even on bumpy roads at high speed I cantake my hands off the wheel and it tracks in a straight line with the steering wheel finding its center naturally.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)