[Mr70]

Yes I read that,and understand fully what Joe wrote,especially these you may have overlooked.

" The answer is some of the same audio equipment was shared among different Chevrolet vehicle lines."
"To keep things simple and costs down,B-body radios such as the AM/FMs were often installed in other vehicles."
"In fact, many Chevrolet vehicles "borrowed" B-body audio equipment at different times in production."

Yes there were A body designated radios as well,but the reality was the above mentioned examples were more common practice throughout many years of model applications then most realize,and I believe this particular radio in question happens to be one of them.
My initial reply was to verify through my own personal experience that Matts 1970 AM "B" labeled radio will indeed fit fine into a 1970 A-F-X body,and Joes explanation was more detailed.
I don't see his eBay references as misleading.