Cheventstein, webasto are not surplus and are not old. They are on heavy heavy truck practically that runs up here in Canada. They come in several sizes, large enough to heat a 18 litre highway truck and cab, large enough to heat a container, small enough to heat a small RV or Boat. Not cheap but a great solution. There are other makes, I saw a web posting on this site just recently but can't remember the name. I think buying and installing on a F350 might be a pretty tricky and costly job. But I am sure a price at a heavy truck shop could be written down if you asked. Probably $2 grand in total I would bet.