If you replace the pan gaskets make sure you get silicone in the corners were everything meets up. I have had leaks there in the past. The last time I changed out the gaskets, I used The Right Stuff on the curved rubber piece and in the corners and have not had any leaks since. Several years now. You just rebuilt that engine, was the rear main seal installed in the right direction? Also you need silicon on the ends of the rear main seal were the rear main cap contacts the block. It really is a poor design with all the pieces that mate together, all potential leaks. If oil is hitting the flywheel, that sounds like rear main seal area to me.
