I don't know if this helps, but an old Hollander Interchange manual shows the following info:
Hollander Interchange #4- 22.5 x 6 with a 6-8 3/4" pattern, factory part#3724641 fits 56 Chev 2-2 1/2 ton and 56 GMC 350, 370, 450 and 500
Hollander Interchange #596- 22.5 x 6 with a 6-8 3/4" pattern, factory part # B6T1015 fits 56 Ford 2T, 600 Ser and 56 Ford T 700 Tandem
No info is given on center bore diam.
