Not exactly sure what to tell you on this, but it is my impression there are two different steering boxes, and both should work. I think the Atlantic British replacement video kind of walks through that. I believe there is a 3 bolt and a 4 bolt. The difference is the gear ratio's and the amount of throw needed to fully swing from lock to lock. Now don't hold me to this, as my research was limited, and fortunately Meridian did not tell me they had two different box's. Had they done so I might have hit a mental vapor lock on that.
FWIW, I have driven a bunch now with mine, and I don't remember having a truck that drove with this much steering preseason/confidence in a while.