There should be a bolt (or bolts) at the top of the jounce bumper. '98 and earlier models had the jounce bumpers mounted on the frame, outside the spring coil.
When I installed Air Lifts on my '98, I let the rear axle hang down as far as it would go and then folded up the air bags and squeezed them in between the spring coils. It was a tight fit, but it saved me a couple of hours of disassembly/reassembly necessary to remove the springs as Air Lift recommended for installation. I routed the air tubing through the frame and crossmember, and mounted the Schraeder valve in an existing hole at the bottom of the left rear quarter panel just behind the mud flap.
BTW, I had my Air Lifts in for five years with no problems. They worked well to level the car trailer I towed with my '98.
Good luck with yours.