Which Ushio bulb? I have the T15 from LL and I measured 173mm from the center of the arc chamber to the bottom of the modul socket. But this could vary slightly depending on how far the bulb is screwed into the socket.
By the way, my entire metal-halide set-up (eballast, bulb, mogul) is for sale or trade in the trading post forum, if you have any need or interest.