Stainless Steel or Titanium with Bronze Rudder Fittings

[parkstone bay]

Hi -

First time I've started a thread - so here goes;
I have a 21 ft traditional-type displacement motor boat with a transom-hung rudder, used in salt water. The rudder fittings, on both the boat and the rudder itself, are bronze gudgeons. (For other clearance reasons, pintles are impractical, though this isn't too big an issue). A number of questions:
1. I will be replacing the existing 2 off A4 Stainless steel swivel pins - in fact 12mm dia x 90mm long bolts - next winter. Any thoughts as to whether these should be Stainless again (A4? A4.80?) or titanium?
2. The boat gudgeons are currently fitted with 4 x 6mm A4 Stainless bolts. Again, any thoughts on the material - stainless or titanium?
3. Any thoughts as to the wisdom/practicality of drilling and tapping in grease nipples? The existing fittings have been metal-on-metal for 45 years, but they now show signs of major wear.
(Titanium fittings seem to be fairly easily available through race/competition car/bike outlets)
Thanks guys!