When was the last time fluids were changed?
Tranny
Diff
Brake
Coolant
Timing Belt? Water Pump? Vacuum hoses? Thermostat? Plugs? Plug wires?
How much wear in U-Joints? Steering? CV-Boots? Wheel Bearings? Any arch left in the rear springs?
How many oil leaks? At this age, I'm guessing both diffs, valve cover gaskets, tranny, steering pump, cam seal, wheel cylinders, possibly crank seal.
These are the things people are talking about. We've all been right where you are and they're two paths to go:
1. play and fix things as they break - which is why so many 4runners are in the shape they are!
2. try and get a handle on all things now
At the very least, I would split your $2k and put $1k to some of the above stuff and $1k to some toys.
I would start out by figuring whats on the truck now. What kind of lift? What kind of gears? Anything else? Generally, getting the truck setup with the right gears, good tires, and a good ride (aka shocks and springs) will give the truck more capability then you probably know what to do with.
Good Luck
BTW - my best mod to date........ 2nd Gen steering wheel
