1969 Dart---Spring relocation with mini-tubs

A 275/60/15 is possible with a 1/2” spring offset and the stock tubs. At that point the tubs are the limiting factor, not the springs.

If you want to go wider than 275, you need the 3” spring relocation and the mini-tub. The 3” relocation with the stock tubs is only good for a 275, same as the 1/2” offset, because that’s all the stock tubs will take.