Pictured is the mainshaft, I think that is what you are looking to set the end float on. When setting my last box I searched high and low and asked the "experts" and all I got was crickets for several days except for one german fellow who thought as close to zero as you can get, but not zero because you need some clearance for oil and expansion contraction etc. In all practicality, with the available factory shims try for 5 to 7 thousandths of an inch. A custom thickness shim is about the only way to get that. I settled for just using a stock shim and ended up with about .010 to .012 inch end float and the box works just fine.