Jim,
I know you are thinking 4x4, but with an open mind, read this thread, it may be an easy route to more of what you want:
http://67-72chevytrucks.com/vboard/s...d.php?t=282398
You really need a modern independent front suspension to make it handle like anything other than old truck, and that alone is going to cost you at least half of your budget. If in the end what you want is a truck that go barreling down unimproved roads and get sideways in the turns a prerunner setup may be your ticket.