The "J" and other similar codes refer to a wheel's 5° drop center rim profile. All of these codes were standardized by the industry's Tire and Rim Association. Each year they published a manual containing all the rim sizes, tire sizes, load and pressure ratings, etc.
I have a pretty nice library of wheel and rim references dating from 1927 to the 1990s when things went on-line. I have Budd, K-H, Motor Wheel, and Firestone/Accu-rude (later just Accuride) catalogs as well as National Wheel and Rim Association catalogs. I've read where guys have offered the opinion that Ford produced their own wheels in some instances, but have seen no reference to support that. It's been my understanding that Ford (as with all vehicle manufacturers) sub'd wheels to the third party suppliers. NWRA and manufacturer catalogs will cross refer their numbers to the corresponding Ford part number. If someone has an authoritative reference showing that Ford produced its wheels in addition to use of the third parties I'd appreciate knowing it. No opinions please, references. If I can help with any research I'll be happy to do so. Stu
