For a real working truck on the farm and such places, the under bed spare tire is too close to the ground. Also the parts that are supposed to slide gets rusty and jams. The track for the wheel carrier (section 7.779) is bolted to the crossmember of the bed. Usually this remains on most trucks. The other 3 pieces were usually removed, put in the barn and the tire thrown in the back of the bed.
Here is a picture of a creation of an enterprising soul (again I failed to note the author). If you don't plan on making a trailer queen, fabricate your own parts.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
