What you are talking about doing is WAAAAAAAYYYYYYY more trouble than it is worth. You are missing cross members and strengthening supports necessary to install the Navigator drive train in your truck. I have done crazy transformations like this to older trucks, and I can tell you that with all the computer operated gizmos in newer vehicles, I wouldn't even try it. By the time you finish fabricating and buying components, you could have bought your grand-dads truck and the navigator.
Just make up something going wrong with the truck (so you won't look like a complete a$$ to your grand-dad), and buy yourself a 4x4
Sidewinder