Can I put an 1992 ford f150's 300 straight 6 motor (automatic trans)in a 1983 ford f150

Your main problem will be with emissions laws.. Federal. The laws vary from one State to another. If you are in Calif by chance, forget it. See- http://www2.epa.gov/sites/production/files/documents/engswitch_0.pdf

Margee wrote "Definitely have water in oil of the 1983" Are you sure that is not regular condensation? After driving my first 300 inline 6 for a few months I thought it had a blown a head gasket. Several people told me then it isn't unusual for the 300 to have a milkly build up around the PCV valve and the oil cap. I have had 6 different 300, 4.9s since and everyone has had this build up.

I am sure it is possible but it will not be a bolt in job. You would need a really good mechanic to do the job. Be sure and get all the wiring and the computer from the donor truck if you decide to go ahead. Get the exhaust too so that you have the catalytic converter.

The bottom line is it is really not worth the trouble and expense.