From the 1972 parts manual, lists both 19 and 22" options. Fender tag, if you have it, should specify core size. If a/c car I only see 22" option though and I would go with a 22" anyway. V,L Val or dart.
'72 a-body 198/225 19" with auto trans - 3574648
'72 A-body 22" /6 engine -
225 - w/a/c...