When you pull the bearing caps off, there are laminated shim packs on each side of the cap. At least, there should be. If they are, all you have to do is take a very sharp razor or exacto knife and carefully catch the edge of one of the shims and peel it off. Be sure to mic the shim thickness before getting it peeled completely off and make sure your removing one shim at a time. The shims are around 0.001" thick.
Before pulling the caps, set up a dial indicator on the headstock casting and let the dti touch the flange on the spindle. Next take a long bar and insert in the spindle and pick up about 25-50 lbs and see how much the indicator moves. Be a good idea to use a tenths reading indicator. Ideal reading is around 0.0015 to .0020" movement. Any greater than this, then you remove shims as needed.
If your headstock does not have any shimstacks to adjust with, then, you have to either scrape off the necessary amount or set up on a surface grinder and remove. May still have to do some scraping for proper fit. If you take too much, shim with precision shim stock to get the necessary clearance.