Here you can see the 204 wheel is actually slightly smaller diameter, which is nice.
I cut the back peice of the 185 wheel off so I could use the horn contact
There are 3 holes in the center of this peice which key into a green ring that works with your signal to click it off.
The holes line up perfectly with the notches in the frame of the 204 wheel, but the green ring still had to be able to key into those holes so it turns with everything. What I did has find some ridgid plastic tubes, cut them to size and glued them in (there are the white peices sticking out of the 3 holes) this let it key into the wheel and the green ring. The tubes sit flush on one side and stick out towards the wheel on the other. The plastic tube was from a balloon, the long sticks they sometimes come attached to. Keep in mind it all get sandwiched together so tension will help hold it all together, the tubes just make sure it stays centered.
I simply added a connector onto the horn wire and it plugged right into the 204 horn switch. After that it's just a matter of bolting it all up together.
Here you can see there is a very small gap, not even a half inch. You can also see the cover I made for the hole the 204 cruise switch, it's just a simple peice of vinyl that had the same vein print. I can take a pic of how I attached it if anyone is curious.
Here it is, 204 wheel in a 185.