wow.
according to your above pictures, the first thing you should do is drain your front and rear differentials and replace the gear oil in them, as they are probably full of water now, unless the vent tubes were extended by the previous owner. which i doubt.
then, if it were me, I would go through the truck front to back and start checking things out like fluid levels, fluid conditions, belts, hoses, welds (especially since its a sas) etc...
cause you never know, the previous owner may have been a tweaker or something.
from there, you need to figure out what you want to do with this truck (wheel it, daily drive it, etc) and build it accordingly.
check out the FAQ section. lots of good info.