13" Large Dial Dimensions

I'm beginning the process of converting my small dial 13 to large dials. I have the graduated dial itself, but what I need to know is the actual dimensions of the large dial bushing for the cross slide. I realize that I also have to modify the screw itself, but that's no problem. I did it on my 9". If anyone has a large dial 13 and has a little time would you be willing to get some measurements for me? I've attached a picture so you know what I'm talking about. the smaller diameter you see sticking up in the middle of the drawing would represent the nut for tightening the bushing in. While I realize I could technically make the bushing any size I want, these measurements would make life a lot easier.

Thanks