[Lynn Eades]

The Circlip that Mark has suggested that you leave out, has the same role as the spacer next to it. I concur with Marc.
When you look at your carrier picture, it is not the correct picture, but it was the one available, so it went in the book.
I think Marc's advice is "bang on" (correct) When you buy a new input bearing, buy the "slot filled" one with the higher number of balls. (13?)
When you assemble the mainshart into the box. Bolt the rear housing up, and measure the clearance with a feeler gauge. It can be .003" clearance to .003" preload.
Example; If you measure an .008" gap, install a .010' gasket and you end up with a .002" endfloat.
As you are using a non carrier box, I understand that the gearbox lid is carrier specific, in that the two bolt lugs on the side are a different length than other Ford boxes.
Make sure that when you install the oil baffle/ slinger that it is in there with the protruding centre toward the bearing.