On a ‘70 Dart Swinger you won’t get 275’s in there without a 1/2 spring offset, it can’t be done with the springs in the stock locations.
Even with the 1/2” offset it will be close, some cars might still need to trim the quarter lip depending on ride height, suspension, and body tolerances. Some won’t, but if your intention is absolutely not to do any trimming I would suggest doing a test fit even with a 1/2 spring offset before you pulled the trigger on new wheels.
Seems like both of you are talking about Dusters/Demons/Dart Sports.
A ‘70 Dart Swinger like the OP is talking about has a full 1” less room than the “sport” body style. Even with a 1/2” offset 275’s are super close on the hardtop Darts.
