I am beginning the search for 'corret' trim rings for my 69 z-11 camaro. Most catalogs have several sizes listed. I know how to determine 14 or 15 inch, but what about the other measurement? ( 7 in, 8 in etc) Can this be done without removing the tire from the rim? thank you for any help

Any shop that installs and balances tires has a tool that will tell you the rim width. The only thing that has to come off is the trim ring, they should even be able to do it in the parking lot with the rim still on the car.