Instead of wheel spacers, you may want to go to wider rims. (Also check tire clearance in the wheel well.) The metric tires sizes require a wider rim than the 8x19.5. A 225/70 is almost the same width as the 8R's but the 245/70 is over 3/4 inch wider on each tire. The wider rims would give you a wider track and also provide the additional offset for minimum dual spacing without using a spacer.
Look at mimimum rim width for any tire you want to switch to.
ARTICLE HereIf you want to compare tire sizes:
Tire Conversion chart