Doesn't the linkage pin to the open hole on the left brake housing or something nearby? The owner's manual should illustrate it. Maybe this page will help:
I've got a 240 with a Super C fast hitch. Since there isn't a rockshaft on the 240 the tilt was entirely free. I bought the exact part Jim linked to lock it level.
The one Jim pictured doesn't have the mounting hardware. I used a pin on the drawbar end (the slotted area) and made a bushing for the other end by grinding down the outside of a Cat 0 to cat 1 bushing for the tractor end.
I'll try and remember to get you a picture when I'm out and about later.
The pin is through the hole adjacent to the slot. This positions the hitch level. I assume the slot is for something like a disc where you want it to be able to float.