Just something to keep in mind..... A 15x10" wheel with 4.5" backspacing will actually move the CENTERLINE of the tire 3/4" farther away from the leaf spring than a 15x8" wheel with the same backspacing. When wheel width changes and backspacing stays the same then the OFFSET of the wheel CENTERLINE changes. This is why I dislike it when manufacturers only list backspacing & leave it up to us to determine offset.
If you can determine how far the mounting surface of your brake drum is from the middle of your tire clearance area (Like the area between your wheel lip & leaf springs, for example), then you just need to divide that by two to determine the offset necessary to center your wheel in that space. After that, you just buy the width wheel you want with that offset number. To hell with backspacing. If the offset is correct, the wheel will always be centered, whether the wheel is 6" wide or 10" wide.
Backspacing numbers suck. :toothy10: