If you need to replace that switch, it is not sold as a seperate item. It part of the tailgate harness which is Ford P/N E3TZ 14529-B listed in the 80 - 86 parts catalog under group 14529. This will get the parts guy in the ball park and should be able to find the 92 part under the same group.
It would be less expensive to go to a junk yard and cut that switch along with some the wire attached to it and splice it into your harness. also, if the harness on a junker is in good shape, tke the whole thing. Watch out for broken wires where it flexes between the tain gate and where it goes into the body behind the tail light.
Another common problem is the connectors that get moisture and either corrode so the connection doesn't make or sometimes the lead going into the connector corrodes until it breaks off. There is one on the frame under the left fender that goes quite often.
Attached is a digram of the circuit for 80 - 86. Functionally it hasn't changed for the 87 and up. I believe in the 9o's they had one less connector. This one has one less connector.