hi i have a 1974 350 with rear seal leak Ive replaced and it still leaks i even off set the seal and its still leaking is there a better seal i could use for a stubborn leak like this. cam plug and oil gally plugs are not leaking and rear seal only leaks when motor is running should i use an offset seal or a double lip seal this motor only has 6 hours on it. and has anyone used these seals if so do you have any part # thanks for the help