Where exactly is the O2 sensor on an 87 Dodge D150 slant 6?

The oxygen sensor on the 1987 Dodge D150 1/2-ton pickup with 2-wheel drive and a 3.7 liter 1Bl 6-cylinder engine is mounted in the exhaust manifold, next to the transmission bell housing. Check under the hood in the rear engine area on the driver's side.