Try this, you will be isolating the rear axle. In a clear parking lot or on a road where you have plenty of room and no traffic. Hold the parking brake release and apply the parking brake slowly and feel for a vibration.
A brake job is a lot more than just installing parts, especially on a 20+ yo vehicle. The hub where the rotor sits against must be cleaned of all rust so the rotor sits flush. The calipers must slide freely so all of the hardware must be removed from the caliper, cleaned and lubricated. If the caliper doesn't slide freely everything gets transmitted to the spindle and into the brake pedal. Honestly on an older vehicle I am doing a brake job on I look at replacement of calipers and hoses.
Also on an older vehicle it's very common for the rears to not be functioning properly from neglect and all of the braking being done by the front which overheats them. I throw wheel cylinders away and install new when doing rear brakes on older vehicles along with the springs.
