best way to get a perfect steering box is to buy a new or reconditioned one. Jon White or the supplier in Galway should have one. Second hands ones are all going to be subject to wear. If you want to go the second hand route I have a selection of steering boxes available...
steering coupling, don't be messing with used ones, new ones are cheap. Get the type with the metal sleeves inside the holes, the ones with the large washers are a balls of a job...