Thanks for all the tips! I went with the trailer idea and borrowed one from a co-worker. That was interesting. Trailer had a medium-fast leak in one tire and was half flat for most of the trip before i noticed. Got the job done though and no mess in the truck!
Bump. Based on this thread, I had my drywall sheet pre-cut at lowes into 2 2'x8' sheets. I placed a plastic painting drop cloth to protect the interior but there was really no mess at all. Also, talking with my wife on the drive home, we think we probably could have carried the entire uncut sheet hanging out of the back window.