There is some oil leaking onto the starter/starter area, possibly from just above it on my 2002 f250 7.3 liter. It's not quite enough to make a drip, bit the area is wet with oil. There is quite a bit of dried oil that has caked on over the years.
What appears to be some sort of breather hole just next to the oil pan, is where I think the oil is comming from. I don't think it is the rear main seal, I just had the transmission rebuilt and a new seal put in (or so I'm told) I have had the high pressure oil pump replaced, oil pressure lines and fittings replaced in recent the past, 20k miles ago.
your valve cover bolts may need tighing up.
Search Ford F-250 Super Duty Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-250 Super Duty Experts