[1986nate]

The SVXi that I have service history from and were dealer maintained have had the belt and pump done at 60k miles, or thereabout. Take a look in the "what have you done to your SVX" thread to see what happens to a water pump that seized up at 88k miles. Considering it's only an extra $120 plus an addition hour or so of labor, it's worth getting it done so that 10k miles later, it doesn't take out everything you've just done. Also, most shops won't warranty a timing belt failure if the pump seizes. I also do all of the idlers everytime. The seals are 50/50 and depends if they're leaking. If they're not leaking, I won't touch them.

As for trans fluid, I stongly suggest 30k miles max before a drain and refill with a filter change. (I realize there is debate about the filter) A lot of people do a drain and refill of the trans fluid every other or every 3rd oil change as well. Doing it more often definitely can't hurt.
As for differentials, wouldn't hurt to change them every 60k miles or so. I've seen plenty that I'm sure were original when doing 4.44 swaps and normal service with well over 100k miles.