283 Oil Leak?

[66gmckid123]

Hey I've been lurking the site for a while, but haven't made any posts yet. I have a 66gmc fleetside, 283 out of a 61 impala. I have an oil leak here's whats been replaced valve covers, intake (siliconed the ends), oil pan, oil pressure switch, and distributor ring. The oil runs down the side of the bellhousing and runs from under the crossmember and drips out the inspection cover. The back top of the engine looks a little wet like the oil breather is leaking, is that possible? I thought rear main, which it could still be but it's running down the side of the bellhousing and drips down from the back of the motor? Any thoughts would be much appreciated
Thanks Andrew