I understand that 351 Windsors have trouble with the rear main seal leaking. I put a 351 in my '91 (a Lightning short block from Ford Motorsports) and it leaked from day one. Recently, the engine was pulled and all of the seals were replaced while it was out. The rear main is leaking again and this time it's actually worse. Anyone have any experience with this problem? Can you offer any advice on a fix?