Slow, Driving Rustoration 1972 Dart

So I guess the starter was correct? I'm not sure why, but mine is different and there is a brace and bolt on the engine block that will not accommodate the correct one. Everything I look up points to this 1972 318 needing the 3258 starter. While the one installed in mine is the one with a shorter field housing, model 3250. There is about a half inch difference in overall length. The 3258 is a higher HP model I guess. Do you think there is a chance that my car has had a motor from another year installed? I've also posted a version of this question in the technical forum.