Re: Diesel fuel leak, bottom of bell housing??
That is the Fuel Restriction Sensor (also called a vacuum switch by Ford). They are notorius for leaking. You can replace it (usually only available from Ford and pricey at $50 or so) or you can get a 1/8 NPT plug and just plug the opening. The sensor lights the Fuel Filter light on the dash and if you are good about changing your filters you can get by without it (most of us have already done this). Don't overtighten it as you can easily crack the regulator block (not cheap!!!). Cheers!
97 F250 SC 4x4, E4OD, 4.10 LS, Basically Stock, Relocated Block Heater Plug, Ext Trans Filter, Tru-Cool Max, I/C Mounted but not Plumbed
SOLD: 94 F350 CC DRW PSD, 5 Speed, 4.10 LS, SBC Con-O, Baldwin Filter, Tymar HPX Hose, 3” DP, Bilsteins, $12 AIC, Coolant Filter, Explorer O/H Console, Trans Temp, Boost, and Pyro, Pedestal Mod, Gutted EBPV