Status update on my original question: I pulled the housing cover and the lower bearing, and instead of cork/paper gaskets I sealed them both with Permatex Ultra Blue gasket maker. One thing that was nice about using RTV silicone gasket material in the lower bearing specifically was that, because the silicone is flexible, I was able to get the same result that you get from swapping out different shims without the hassle of swapping out shims.
What I did was:
- Clean the mating surfaces
- Apply gasket material to the bottom of the steering column and around the bolt holes
- Carefully insert the lower bearing assembly (make sure it's right-side-up)
- Tighten the bolts gently until the silicone spreads out across the flange surface
- Wait 1-2 hours
- Remove each bolt, apply Permatex thread sealant, reinstall with light torque
- After all bolts are sealed, tighten down the bolts in an X pattern, testing the motion of the steering wheel about every 1/2-turn
- When the wheel starts to get hard to turn, back off the bolts slightly
- Wait 24 hours before refilling with lube
No leaks so far, but it's only been one day. Too early to tell whether this approach will work. Will update after a couple weeks.
Separately, I adjusted the sector shaft thrust screw all the way out, applied thread sealant around the threads as best I could, then screwed it back in until the end play was removed. I think this was a major source of the leak.