Well that is the most expensive heater offered. There are several people here who have rebuilt them and converted them to 12-volt if required. There are even reproduction cores available now for them $$$. Here is a picture of all the parts required to install one. If you don't have them some are reproduced but not all. The original switch for these is the second picture.

http://www.flickr.com/photos/advance-design_parts_co/8129470099/in/set-72157631868452754
http://www.flickr.com/photos/advance-design_parts_co/8129352382/in/set-72157631868452754

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr