I am 63 years of age. I have a business visa but would like to be able to work in China.

Geoff, you can possibly convert M type to work Z type at the exit and entry administration of the local PSB.
You should first prepare all the required documents for work Z type including your passport and copy of its data page, the application form attached with a passport-style photo, valid temporary accommodation registration form, alien employment permit or foreign expert permit, and an invitation letter from a duly authorized unit. Your employer will get you the last two documents.
And then submit the application to the exit and entry administration to change M type to Z type.