External reservoirs (and larger shock bodies like the 6112) main benefits are more oil and/or oil cooling which directly impact how Long the shock can be pushed hard before it fades (from heat). Might also get a little longer usable lifespan, but I doubt it the more I think about it. Wheeling doesn't heat shocks, it's a slow and methodical thing (usually). Think more like extended washboard roads on the normal human side of things, and Baja style whoops on the superhuman side. I drive a fair bit of washboard, it was the main reason I opted for the 6112/5160 over the 5100's.

As for bushings, front and rear upper and lower control arms, swaybars/end links front and rear, steering rack, and panhard are, I think, the majority. Then there's the body bushings, which I haven't done yet but they're on the "want to get done" list.