15x8 4 1/2 BS 275/60 stock spring location

Would you know off the top of your head what I'd be able to fit under the car if I did the relocation and mini tubs?

Easily the 275/60s like you're wanting, probably up to a 315.

But I think you can fit the 275/60s with just a spring offset and picking the perfect rim size and offset. There has to be someone here with a Dart or Scamp that's done this tire size without a mini tub.