[racer_d]

There are two items one can use to get a wheel to fit

1) Spacers - Often thin "disks" that sit between the wheel mounting face and the wheel itself. 3,5, and 7 mm are popular sizes. They are sometimes available in thicker sizes. Depending on the thickness, new lug bolts would be needed, to ensure the correct amount of thread is engaged.

2) Adaptors. These are more common, especially when dealing with large thicknesses.. say 1-3 inches. These bolt to the existing wheel hub and the, on the "outside" have threaded holes for your factory lug bolts.

While fine for regular street use, and occasional sporting use, both should be avoided for track driving. At the very least, I would encourage more vigilant watching for cracks and stress on the wheel hubs.

Ideally, you should locate and acquire rims of the correct offset, then these other solutions are not needed.