Ok, so you have fuel from the HFCM on the drivers frame rail to just forward of the engine crossmember, up to the upper fuel filter at a Banjo bolt with two copper washers. From the fuel filter assembly you've got two hard lines, attached with banjo bolts and copper washers at the filter housing and the cylinder head. The fuel passage runs the length of the head and is plugged with a single copper washer to seal it. The filter housing has it's plastic cap sealed with an o-ring and on the front of the housing there is the fuel pressure regulator which seals to the housing with a molded o-ring. The fuel return line then follows the feed line back to the HFCM. Just about at the same level as the exhaust manifold there are two quick connect fittings and some braided flex line, the fittings have o-rings in them to seal the connection, as do all the quick connect fittings on the HFCM and at the tank.
That is your fuel system, if you check all of the points mentioned and there is no sign of fuel loss, then you will want to look closely at the bellows on the up pipes for signs of exhaust leaks, also the EGR cooler v-band and turbo to y-pipe v-band connections as it is possible to have a misalignment and a small exhaust leak from those points. Unlikely to be the exhaust manifolds at the heads, but still give a look there, especially the passenger side as it's closer the the cowl vent, and inspect the connections at the up pipes to the exhaust manifolds to see make sure you don't have any broken bolts.
It's quite a lot to check thoroughly, but can be done in an hour or so, and a cell phone video camera with a light can aid you in looking at areas that you simply can't see because you can't get to them with anything more than your hands. And if you have to use your hands, buy a pack of nitrile gloves, play proctologist and stick various fingers in dark places. When you check your fingers on the glove, if you see black soot, or a fluid that ends up smelling of diesel, well, then you've found the source of your fuel smell.
Good luck, keep up posted of your findings!
The Current Truck (Oct-2013 to Present):
1999 (Early) F-350 Lariat, CCLB, SRW, Black/Tan
7.3L Powerstroke, 4R100, 4x4, 3.73, 37x13.50-18s, '05 Axle Swap, 6" Fabtech lift, GTP38 "D66" turbo upgrade, SCT 4-position chip with custom tuning by me, Straight Piped 4" down pipe through 5" dual stacks, N-Fab full length triple steps, Pro-Tech cab guard and tool box, louvered 5th wheel gate, Hella 500 Fog and Driving lamps, much more to come...
The one I'll miss, (Mar-2009 to Jan-2014):
2000 Excursion XLT 4x4
6.8L V-10, 4R100, 4.30, 285/75-18, 271whp / 388wtq
The one I won't, (Jul-2005 to Sep-2012):
2005 F-350 XLT, CCLB, SRW, 4x4 FX4
6.0L PSD, ZF-6S650, 3.73, 35x12.5-18, 4.5" Lift