What kind of rear end on a 75 dodge dart swinger 318 2bbl?

A 1975 Dodge Dart Swinger with a 318 2bbl engine likely had a 7.25-inch 10-bolt rear end. However, there's a small chance it could have a different axle depending on options chosen at the factory (like a higher performance option). To be absolutely sure, you'd need to check the vehicle's build sheet or look at the axle casting number itself.