SO there are a couple of items there.

1. The Woods shafts are fabulous but I wouldn't personally bother changing unless there was damage (not just the Uni J) or more likely for increasing the spline count (just means bigger diam shafts). It won't hurt but I don't see the need.
2. The Uni J will fail for any number of reasons not just because of a shaft issue. Actually I understand that the Uni J is intentionally designed as the point - it's a lot cheaper replace than breaking something else. Most common cuase of fail is to do with alignment through the joint - "pinion".
3. Pinion is adjustable if you have adjustable control arms. Also with adjustable control arms caster is adjustable. What is NOT adjustable is the angle between pinion and caster (or you replace the diff as it is a manufactured in angle). Sometimes it means you end up looking for a compromise between the two and live with wearing through the Uni J.

Hope that makes sense and btw I am no expert so happy to be corrected by anyone with input.

Dru