The impeller source is the same for both types. You just have the short 5 bladed impeller.
Does your impeller housing look like this?
Then you probably need this impeller. This one is 1/2in thick and around an inch and a quarter across the top.
It's been a while since I've had my Eska lower end apart, but I believe the shorter impeller has a notch in the metal core that one end of the loose pin that goes sideways through the shaft rides in. I believe the impeller should just slide off the end of the shaft with a little gentle persuasion. I think that the impeller housing is what holds the impeller in place, which holds the cross pin in the shaft, when the motor is together. I don't remember any steps in the shaft itself, just splines and that hole for the pin.
Hope this helps.