My guess would have been for a gen set...as far as a return line I have seen some fittings you can add to the fuel fill line....check it out:

http://www.cpperformance.com/p-16582...k-adapter.aspx

I don't think I can get to the hose, looks like bung will be easiest.
Brought her home Sunday!! But had to fly to ATL for he week!

Not sure what HP you have. If you upgraded the motors/pumps but I had to drill my Pick up hole (single engine) out and tap, might of did my return too. I did it like 8 years ago and forgot if I did return hole. I did it due to recomendations of the fuel pump maker and bigger engine. Also made a bigger pick up tube. FYI should be a check valve in that elbow which can restrict flow.

OK, I was going to pull off to match up as I need to know what size it is along with the return lines. Oh and match up to a Y coming from both.. stock 385s...

The fitting that screwed into the elbow had the valve on my 25 ol, but I will check.. thanks

I changed all my lines to meet the size requirements. Aeromotive pump, regulator, filters (before and after pump), check valve, hoses and fittings I was somewhere around 1k. And this was a single engine.