Jo han was very much doing "Job work " for several outside firms in the early 1980's . I had friends within General Motors confirm that , and they weren't assembly line personnel . In addition , Jo han also did some arm rests for Chrysler as they had access to the chrome plating machines too.
I understand that Johan was pretty much a side business for John H. His main business was contract runs of injected molded parts for the auto industry. Perhaps that explains some of the odd color plastic runs on kits.. pellets left over from a run of arm rests?
I also heard that in later years that they Johan line wasn't a full time thing. When things got slow in the main business, he'd ferry a group over to the Johan plant to do busy work.