What would cause rear brakes to get abnormally hot and smell like burnt rubber after a break change on a 1995 240sx?

Sounds like possibly seized caliper sliders or the piston is not retracted far enough (assuming the car has disc brakes in the rear), if the parking brake actuator is built into the caliper on that model, you may have to rotate the piston back into the bore to release the park brake, if it has a separate park brake, make sure it is adjusted properly and the cables are not seized.