I have 2, and I am running one of them now . . . . they have a larger diameter center hub and cone and they hook up real well. . . . . . . Yours looks like it has been bead blasted but originally they were powder coated.
I doubt any one makes a short cone for it so it may not be ideal for a Freestyle ski. They were a really good pump for racing before the Skat pumps came out.
The stock drive shaft and bearings fit right in and it uses standard SJ impellers. The vanes are also set further forward to decrease the gap between them and the impeller blades (works the same as a set back prop)
EDIT: I don't see a pump cone in the pictures . . . . . . . it takes a screw in cone that fits only this pump. If you don't have the cone then you could have one machined for it and have them make a short one for you while they are at it.