If you run out of adjustment with various boltheads on an existing bolt you can swap out bolt bodies until you find a longer one which will get the headspace within tolerances. The next step is to file out the new bolt s/n,re-stamp with the rifle's s/n,and then re-blue or re-park the bolt. I've done this with a couple of Long Branches and it works out very well.Nowadays it seems easier (and cheaper) to find a replacement bolt than a long bolthead.
That is BAD advice! L-E bolts can't simply be swapped, unless you have several to choose from and can find one whose lugs bear evenly. Usually the bolt that guys think is longer only seems longer because only one lug is bearing, thus forcing the bolt farther ahead in the action. If bolt bodies came in different sizes, the firing pins would have to, as well. I have and have had dozens of L-E's, and all five bolts in my No.4's ,as well as six spare bolts in my parts box are the same length. A mix and match test showed that only one bolt was able to interchange directly, due to the lugs bearing unevenly. REMEMBER, in the rear locking Lee action, BOTH lugs must bear!! The common misconception seems to be that the solid rib does the locking, and the small lug is merely a "safety lug". That is NOT the case! A poorly fitted bolt will, in time, match itself to the rifle as the one bearing lug compresses its seat. Of course, as it does so, the headspace opens up again. Then you're back to square one. A mismatched bolt could even be dangerous with hot loads.