Best thing to do is get the engine looking showroom CLEAN.
Also, you can buy a Leak detector kit that comes with a green dye and UV light, you put the dye in the oil, and the UV light hits the dye in the oil that has leaked and you can trace it back to where it's coming from.
So it could be your Top oil seal, bottom PTO oil seal, oil pan/sump gasket leaking, or on of your valve covers leaking.....
