Andrew Blesi
Member
My 4.0 cratered at 230,000 miles after the timing chain had enough. I replaced it with complete motor from Promar Engines. I rate the people at Promar and their product as AAA+, I have just over 50k on the Promar engine not one problem. They also added an oilier rail atop the valves and balanced the crank.
http://www.promarengine.com/index.php
http://www.promarengine.com/index.php