My solution it to collect lots of spares. Then if something goes to heck you have a quick replacement to get you by. I have started stocking a couple re-man alternators, I try to keep a few starters around. PS pumps, ignitors, distributors etc. Part out as many of these trucks as you can or scrounge wrecking yards for the bits and pieces. Have a shed full of it.
As far as things like the timing chain, water pump, probably when I do a rebuild most of the time unless something goes bad then I take the opportunity to refresh whatever I can justify when I have my engine opened up. I plan to rebuild before spinning them out these days.
One thing on stuff like water pumps, fuel pumps, oil pumps, timing chains and tensioners: I have tried the aftermarket ones and they fail pretty quick. The Toyota stuff or at least higher quality Japanese will last like 4-5 times longer.
