75 rr or 73 sport?

one thing and one thing to look at here and that is avalabilty of parts! both of those cars will not see value for a LONG LONG TIME.... so the next thing that comes to mind, is what is going to be more readily avaliable parts wise? a 1975 B body or a dart sport? the answer is simple the A body has far far far more parts being re-poped and there was way more A bodys built from 1970-1976 all wich allow parts to be swapped, rather then a 2 year car like that runner/fury/coronet you have there