No, I'm too much of a hack for measuring. It's not really a critical modification, either you can shift or you can't.
Only the rear shift rail needs to be modified. If you figure out how the detent rods move, you can pretty much see where you need to grind. I just used my 4" grinder, then finished with my dremel and a small grinding stone the same size as the detent rod.
I should mention, only the t-shift case needs this mod. You can get 2low and front wheel on the j-shift without doing anything more than twin sticking. The j-shift will also let you get one axle in low and the other in Hi.
Anyway, in the first picture the rails and detents are layed out in the nuetral position. If you tried to shift the front axle, the detent rod would move and contact the rear shift rail, preventing shifting. So you have to open up the groove on the rear shift rod.
You could always just toss the detent rods.