1990, V belt drive.
View attachment 1716080623
Tough to get a pic of the pump itself with all the accessories on the front of the motor, but in this pic you can clearly see the pump fan, which is standard rotation.
View attachment 1716080624
All the same part numbers as a '91.
The serpentine drive on the '92 and later Magnums:
View attachment 1716080625
Maybe you got a real late '91 that may have gotten an early Magnum motor, but the LAs were V belt, standard rotation.