Rear main oil drain pipe size

[trades707]

Pulled the pan on the 48 V-12 in search of source for low oil pressure. Find lots of oil on everything, but the drain pipe on the rear main is missing. Anyone have an idea of what size pipe is needed? I suppose it would be best if pipe reached into oil sump.
The engine has a Ford rear seal, slinger groves are ground off crankshaft. Engine also has a PCV valve on top catching vapors under intake and routing to carb base.
Thanks