This is a 8 year old thread. The rear main seals on the 7.3 engine very seldom goes bad. Any oil leak up on the top of the engine which is very common will drain down the back of the engine and look like it is the rear main but it is usually a problem up on top.
Just happened this way at work. Thought that it was
appropriate to call this the Ford family - a F150, a Ranger, and my Super Duty PSD!
(That's Daddy Ford to y'all!!)