Fan ring

I have sanded down the fan ring a little and it now fits into the shroud much better. I have a slight problem in that the fan ring sits a little too far out, so I will have to space out the lower pulley a little. There is nothing stopping me putting the bottom end together now. Trouble is once I start doing that, i need the place to be very clean, but I am worried that I will need to do more mods to the case etc after putting it together.