Realize that an overdrive will not make your F134 Jeep highway capable. Power is torque times RPM, and lowering the engine speed reduces the power produced. You do not hae enough power, regardless of engine speed, to propel your Jeep at modern highway speed. This is a problem intrinsic to the F134 - you are already near the RPM and power limit. As built, the F134 is right at the boundary ... not much room for improvement.