This should make a -10an or 5/8" return line like the one in the DIY oil line sticky. These parts are from
http://www.mcmaster.com
Hose: just like the feed line but 5/8" ID and 3/4" fixed male threads on both ends. I don't know what length is needed.
#5723K181
Fitting: 90 degree female to male swivle elbow. Just like the one used for the feed line but 3/4" threads. This sucker is 2" long so it should give good clearance to the oil pan.
#5340K37
3/4" seems like awfully big thread to have to work with but if you want 5/8 ID that's what you get. Is this typical of return lines?
Anyway, that's what I came up with so far. I think I have picked the right stuff but I have not ordered these so buyer beware.
Second opinions and additional input are welcome. Perhaps If this bears out it would be good to add to the oil line sticky.