Check the valley on top of the motor. You have a drain hole on the back side of the engine on the passenger side that drains any oil/fuel down the back side.
Early 1999 F350 AUTO 4x4 CC LB DRW 4.10 6.0 trans cooler, Front hitch, 2,000 hubs/ brakes, Bilstein shocks/steering stabilizer, Diesel site coolant filter 203 thermostat, EBV delete, new O-rings, new Oil cooler, RIFF RAFF FRX, Glow plug led, Pillar gauges, Lighted cupholder, Painless wiring fuze block, Harpoon/hutch mods, Removed axle blocks. Air bags, 5 wheel hitch, In bed 7 pin plug. Spare tire key delete. KLHANSEN on speed dial. 75,000 as of May 2019