Don't forget to put the oiling plates under the front bearings.
The measurng is a bit of a guess with the bearings rocking and whatnot. I measure from the inside race.
I don't use a gasket. Never had an issue for it and it takes a variable out of shimming. I think they work best on the tight side. I leave the input shaft seal out until I shim them. It's easier to tell what is going on with your shim job that way for the seal sometimes dragging a little.