Oil leaks down to rear crankcase and drips from there. Any suggestions as to source. I cannot see valve cover without...

No, if the case behind the engine and to the rear of the car is the transmission. As if mentioned, there is a tube bolted to this case by a bolt which I tightened. The oil accumulates at the bottom of the drain plug and surrounding oil pan area and also on the heads of the front oil pan bolts but the area above is dry. Hope that helps.

I have determined the oil leak seems to be coming from around the oil pan gasket or possibly from the rear (car rear) from a tube or pipe that is fastened toward the rear by a bolt. This is behind the engine. Possibly there is an o ring or gasket there that is leaking. I was able to tighten this bolt a half a turn or so but still seems to be oil sepage there. The leaking oil gathers right at the drain plug which I also replaced with a new Ford plug. I added a gasket sealer to the crankcase oil and that did not seem to work although the drip may have slowed either from that product or the tightened bold. All the crankcase bolts seem tight.