In doing this I lost the slide which prevents the lens from turning which is why the grey mounting plate has a pin in it. The top plate which the lens mounts on will have a bracket which locates over the pin - a bit like a large Nikon pre-AI metering tab. this wil stop the lens rotating as the barrel is turned and allow the lens to move in and out instead.
Trying the lens out on my speed graphic, it only seems to need 6-7mm of movement to go from infinity focus to about five feet. The helix from the Minolta lens seems about right based on its distance markings. If it's not right, I will stick a new scale on it but being such a wide angle, I think there is a bit of room for error. As long as I get infinity right, I think the rest will fall into place.