If you didn't say you had already done the front main seal I would bet on that since it will sling any oil that leaks there on the compressor. Sure it isn't still leaking there?

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k