heater blower motor

Has anybody ever replaced the heater blower motor with a more powerful blower? I had a 78 CJ at one time and replaced the blower motor with one from a chevy and what a difference. I was wondering if this could be done with a XJ. And if so what motor? 90 XJ 4.0

more than likely the heater coil and evap coil are clogged with crud which will kill airflow pretty sure they all spin at near the same rpm