I have a steering box I got from Keith after he'd done all the seals and painted it up, it's bloomin lovely.
No, without some expensive equipment it has to be done after fitting, namely adjusting the screw after you have centered the box, i have a resealed box here in a rather nice pink, but its something you can do yourself in an hour if the box is off the bus
Interestingly I brought a new early steering box that had the adjustment screw painted over and it was as stiff as a stiff thing. Consequently I think people perhaps under-adjust them and that leads to the wear?
Keith It you have any kits still on the go I'll take one, my postage may cost more BT449JN. If you PM me the details I will sort out payment. Cheers M.