Latest tire 1970 Swinger with mopar off set shackles can I fit a 275 tire?

The only way you will know. Is if you get under there and measure.

Not only does many of our cars come with non-factory rear ends. Meaning it might be wider/narrower than a stock A body rear end. Even from the factory sometimes the rear end was not centered properly. Some guys have seen up to 1/4 difference in difference of clearance between the rear tires. This can affect what you can run.

The best thing to do. Is get under and measure your hard points. Measure from the wheel mounting surface to the farthest out hard point. Usually the fender lip. Then from the wheel mounting surface to the farthest in hard point. Usually the spring/shackles. These two numbers together will give you the total section width you can run. These numbers separately will tell you how much back space you need.

For example. Lets say from wheel mounting surface to fender lip is 4 inches. And from wheel mounting surface to springs is 6 inches. You can run up to a 9 inch tire. This will leave you a 1/2 extra clearance on each side. You WILL want this. The rear end does move side to side, especially in hard cornering. Some guys run as little as 1/4. But you will get occasional tire rubbing.

Now for back space. A 9 inch tire will probably want a 7-8 inch wide rim. Lets say 8 inches for ease of math. You want 3.5 inches of the TIRE beyond the mounting surface. And 5.5 inches behind it. That means you pick an 8 inch rim with 5 inches of backspace. This will give you 5.5 inches of tire behind the mounting surface. And 3.5 inches of tire beyond the mounting surface. This is just an example. Your setup will probably be crazy different.

Clear as mud? I know in your case it can be difficult to measure since you don't have the offset kit in. But you should be able to mark where it would be and figure it from there. As I said. There is no "one size" fits all with our cars. The biggest problem being how much people have touched them before we get them. Who knows if that rear end is wider, or shorter, than it should be. Or if the springs are in the right spot. Or if the rear end is actually centered (often it isn't). I just hate to see guys go out and buy a set of whatever tires/rims, go to put them on and no bueno. It's easier to get under there and measure.