I too am doing a rear main seal. I have a neoprene seal (two sets, in fact, since I fully plan to screw up). Do I have to remove the oil pump pump? I kinda want to clean out any sludge, but I can't find the gasket sold separately. I see one pic from old-tank (at http://www.buickrestorer.com/rearseal/rearseal.html) and it sure looks like I do.