If it's just a basic refresh, buy a low mileage Explorer/Mountaineer engine, sell the GT40P heads and intake and recoup most of the cost. Then you'll have a decent foundation to work with, while you save to build a "good" engine, with the parts of your choice. $900 doesn't go very far when rebuilding. It might get you a hone/re-ring and some new bearings, but not much more.