Been a while since I put a motor together, and yes, every one had a dribble somewhere.
Here's what I would try.
Make sure the threads in the block are clean.
Make sure the pan and windage tray are flat on the sealing surfaces.
Dry fit them to the block and see if all the holes line up and the surfaces match.
Use a good sealer and glue the gaskets to the tray, using a bunch of clothespins to hold them in place.
dry fit again to make sure the gaskets aren't hanging up anywhere. Trim if needed.
Apply a small amount of silicone at the areas where the gasket surface changes (front cover and
rear main) to help seal these areas.
start all bolts with locktite and slowly work from the center out, easing up to a torque spec.
recheck after a few heat cycles.