I did a post a while ago; re this- when I was having issues fitting the genny belt pulley(s). Almost 0.020" !
I considered moving the gear on the shaft as b-Bil says, but if I were to go one way, the back of pulley would rub, if I went the other way, the pulleys/belt-sprocket/chain would be out of alignment, so I decided that as there's no apparent need for end-thrust on the gear, a bit of end float won't matter, as the belt/chain will self-align everything, and as there's constant change of 'rotational thrust' on the gears, it's a constant self alignment- in theory, and so long as the gear is located appropriately!!
And it also depends on the thickness of the inner gasket.
I may be wrong.
Cheers,duTch