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Being a '95 you may have a different problem. '96 and later 7.3's have a standpipe in the hpop reservoir cover the prevents the oil from draining back through the ball valve. '95's do not have the standpipe. If you search this site you will find at least one method for modifying your reservior to include a stand pipe.
Since mine had the standpipe and I already replaced all gaskets and the check valve and it was still leaking I was left with nothing else to replace but the pump. A reman pump cost $308 + $300 core charge. I got the 99.5+ pump since it has higher output. The problem is finally fixed!