O2 sensor(s) would be on the driver's side. The sensor(s) are in the exhaust, one between the engine and catalytic convertor and if a 2nd one is present, it would be after the cat. Passenger side of engine has the knock sensor up between the oil filter and the fuel filter, the oil pressure sender or switch below the oil filter as well as temperature senders for the ECU and gauge.

On the tranny, reverse light switch is on the driver's side next to the oil fill plug. On the t-case, passenger side is the 4WD switch and the speedometer cable or VSS and wire.

There are often extra plugs on the engine, mine has two on the passenger side that don't seem to go anywhere.