The fans on the W124 blower are extremely delicate!
Clean the rust off of the shafts with fine sand paper (400 grit?) so that you won't chew up the ID of the fan when you do get them sliding off. Also observe the direction of the fans and measure how far they are on the shaft so you can get them back on in the same position.
Best thing would be to pay the extra and get the motor with the fans mounted.