When I replaced the Z24 in my D21 with a KA24E from a D22, I ended up replacing the PS pump with the later one. THe older one came close to fitting, so you might be right with a minor mod.
Mate, that was last May. Tried to sell it on ebay and got no offers.
And I just cleared out my shed in preparation for Ului last weekend
I'll have a look, but doubt it's there still. Apart from that, it's still only the pump. You need th reservoir, hoses and the bit that connects to the steering box.