Rick - I've been continuing to search through old threads on the topic and have more to share, but probably not until tomorrow when I can get fresh start. I will note that somewhere in one of the distant past topic threads, a Bolter mentioned that he knew of 4 different style of the early under bed sliding track tire carriers. So far I've come across pictures of at least two of those designs, with yours bolting to the underside of the bed wood being one.
More to come tomorrow...
