The 15" steel wheels and trim rings were only utilized from '70-72 on the Mustang and '70-71 on the Torino. So finding a nice set 50 years later can be a frustrating and expensive search. The Ford part # for the wheel is D0OZ-1007-A. Although this wheel has an engineering ID #, Ford usually only marked the steel rims with a letter or number near the valve stem hole and a paint daub. That would be the letter "B" and a green paint daub for this wheel.
The 15" x 7" wheel trim ring is D0ZZ-1210-C (D0ZA-1210-D, G). This trim ring was sourced from the '70 Boss 302, the first of the first-generation Mustangs to use a steel 15" x 7" rim. All trim rings had a brushed finish. Ford did not use a bright or chrome finish trim ring on these wheels. There was a running change on the valve stem hole. There were reports from the field that the original trim ring with the round hole was cutting and damaging the valve stem when removed for maintenance. Engineering released new trim rings with an oval or "Racetrack" shaped hole, making removing the trim ring easier without damaging the valve stem.
The center cap dog dishes were the same size in the carline regardless of rim size. The difference is a brushed finish for trim ring-equipped cars and a shiny or chrome finish for non-trim ring vehicles. The original center cap is D0AZ-1130-G (D0OA-K, D0ZA-J) replaced by D5DZ-1130-B (D5BA-AA, BA). Since the center cap is a corporate piece used across all car lines, it can be easier to find. The trim rings do show up occasionally, but versions with no curb rash or dents are few and far between. I have seen pristine or rare NOS versions sell for $1,500.00 and above. To my knowledge, there are no exact repos of this trim ring available at present.
Since the Ford wheels are no longer available, I would suggest Summit for the Wheel Vintiques version,
https://www.summitracing.com/parts/wvi-62-5712044
or Coker Tire
https://www.cokertire.com/wheels/steel-wheels/oe_style-15x7-5x4_5.html
There is contact info for each site if you need additional information or clarification on the wheels and if, by chance, any trim rings are available.
I know this is a lot of number and letter salad to digest, so let us know if you need any further info or clarification!