Jeff,
I did a search on "radial" in the general forum and found this (exactly what you found):
Cooper 4 ply SRM II
LT215/85R16 (with tubes, on original 16" rims)
Other manufacturers should also have a similar LT radial. Usually it is not on display but it is in a sales brochure or in their on-line listings. The brochures and on-line listings usually give dimensional information.
As I recall, the original tires had a loaded diameter of between 28-29 iches. I think that Cooper radial was supposed to have a loaded diameter of about 31 inches but on my rims the diameter is a little larger (maybe due to narrow rims). The larger diameter results in lower rpm.
Good luck,
Tim
