Part Type: Fuel Tank Cap. OE Equivalent Fuel Tank Cap. 1973 Ford F-100 Engine: 3.9L L6 GAS;BedType: Fleetside; W/O Evaporative Emission System; With After Axle Tank;. 1973 Ford F-100 Engine: 4.9L L6 GAS;BedType: Fleetside; W/O Evaporative Emission System; With After Axle Tank;.