Here's some info on the wheels you're looking for
http://www.stovebolt.com/techtips/wheels/Commonly (or uncommonly as it may be) found on 56-59 Chevy 1.5 ton trucks.
Do note that these wheels are only 5.25" wide, and although I've had no problems mounting 9R22.5 tires on them it's not recommended by the tire manufacturer, I really should have a 6" minimum rim width.
I seriously doubt you'll be be able to mount a 245/75 tire that requires a minimum 6.75" wheel on a wheel that's only 5.25".
There are other options out there, having some new centers/bolt pattern plates welded in ordinary 22.5" wheels has been done and is functional, although looks a little odd.
You can investigate using ordinary 20" wheel dishes on new 22.5" rims, the diameter works out, but back spacing may be the problem, although if you need wider wheels any how it may work, worth measuring and checking, but I wouldn't hold my breath.
The cast iron Dayton wheel adapters which are even harder to find could be an option, then run 7.5" Dayton wheels, or 6.75" if you can find them.
What vehicle do you want them for, got any pictures?
Grigg