I think the Frontier uses the same suspension as prior D21 Hardbody pickups, and thus uses a torsion bar instead of the standard coil spring. Lowering the vehicle, would involve changing the amount of pressure applied to the torsion bar at the mount end. This would involve a retro or custom design to allow the Torsion bar to ease out of its tight constaints and allow a lower ride. That might cause a ground clearance problem with a custom designed mount. It is probably easier to just go with 50 or 60 size, but smaller diameter tires and std size or smaller wheels. That will lower the vehicle about 3-4 inches. Laying it to the ground, you will likely spend upwards of $2K or more to get it lowered right, with an airbag suspension. I am new to the Truck scene but I have a D21 that Iam working on and am intending to do what I recommended, with either 215/70R15 or 14 inch wheels, or 215/65R15 or 14. I Still have to find the right wheels, (I'm looking at American Racing since they are relatively inexpensive, yet produce nice designs for 4x4 Trucks). Also, looking to update the 4 cylinder with a newer 90-96 6 cylinder Multi-Port FI motor ( good milage and power, and torque for 4wheel drive).