Well, I now understand. That wasn't explained on any site I found selling tires. I looked it up at Cooper Tires for my existing set (ATR). There they have a list which discloses the "LT" range of available sizes. Very interesting...
But what is the rim width I have? 7"? Do you know that? There is a lot of tires (in old sizes) and wheels listed in the manual, but I don't really know which rims I have. I don't think these are factory provided as there are nowhere 17" rims stated for the 1965 C-series. Only 17.5" as far as I can see. The mounted tires are definitely 255/70R17. I would measure it if the truck wasn't in the shop right now.
Many thanks for your patience and your very good help!
Edit: Bill, what size are the rims/tires on your truck? I've seen your photos and it looks great!
Last edited by Joern; 10/29/2011 12:03 PM.