My '96 with a 351 seems to have an oil leak going. I degrease underneath around the oil pan and up between tranny bell housing each time I change the oil. I noticed when the truck was setting level, I had some accumulation on the floor. In the driveway when parked (on a slope) I never see this. The problem I had on my old '94 with a straight six was a rear seal, but it coated the underside, tailgate and back window. I don't see any of this. Is it a possible rear seal issue? Any thoughts? I have been running synthetic oil in it since it was a baby. Thanks a bunch!