Usually Ross, it is both races that get socketted. Hence my suggestion to get a new inner, and regrind the old special profile outer.

I changed my Atlas from a plain bearing head to a taper bearing one, and the second hand head must have stood preloaded for a few years. It was like trying to turn over a ball bearing detent fixture, it jumped out of one impression and clicked into the next one, hence that is when I found out about grinding and costs of bearings for the head.
BTW, if you used a plain bronze bearing head, you would find that the surface finishes on components are far superior to a tapered bearing head. The taper bearings were introduced to up production rates as they could have a faster running spindle, what you gain in quantity, you lose in quality. I noticed a definite quality reduction when I swapped over.

Another thing worthy of note, the bearings should be oil fed only. If you try to pack a taper bearing with grease more than half full, you run the risk of 'hydraulicing' on the rollers which can lead to roller damage, little and often for oil lubrication, if necessary, fit drip feed oilers if you can.

I can't really understand about what you are saying about the saddle gear and rack, but there is an adjustment cage on the back of the apron that allows for slacker or tighter engagement of the gear. There is an adjustment bolt for it just to the rear of the handwheel. that allows you to move the cage up and down. Also, you will find that if you slacken the two top apron screws, you can shim in the joint to 'kick' the apron in whatever direction is required, but you must ensure you realign the leadscrew afterwards, so that it doesn't deflect when the half nuts are engaged. That is done at both ends of the leadscrew, by shimming up and moving about the reversing box where it bolts to the bed, and the same again at the other end at the break away sacrificial support for the leadscrew.
BTW, don't ever be tempted to replace that break away bearing with anything else more solid, that is a safety feature to protect your very expensive gear castings and apron area plus leadscrew in case you ever have a massive jam up, where the saddle stops and the head carries on turning. That piece is designed to break under such circumstances, when the leadscrew tries to carry on turning, and screws itself backwards thru the half nuts. You should see that it is cast with weakening cut out 'wedges', to control how and when it is to break.
I have seen these lathes where people have made massive bearing block replacements or had a broken one welded up. A very bad idea.

John