Tires and/or wheels out of balance or bent? Rotor warped?
It could be the U joints from the transfer case causing the problem.
front passenger site
The engine may vibrate causing the front bumper pab=nel to rattle.
Near the front of the gas tank
Dana 44 Twin Traction Beam
Your rotors are either worn unevenly, warped or both. Replace them next brake job.
For a 1989 Ford 302 cubic inch V8 engine : The # 1 cylinder is at the front / passenger side of the engine firewall 4 - 8 3 - 7 2 - 6 1 - 5 front of vehicle
On the 4 cylinder its at the front of the motor On the V6 its on the passenger side of the motor , front cylinder
It could be your radiator fan.
Measure from center of front axle to center of rear axle.
It's looks like this ->O
20 gals. front 18 gals. rear