Joern, mine are 15x8 Chevrolet Blazer Rallyes with a 30x9.50x15 C range Michelin LTX M/S tire.
Just judging from your pics, the wheels you have are either aftermarket or from a later truck. Only real way to tell would be measuring them, but eyeballing it, they look to be a 7 or 8 inch. Either will be fine with the tire sizes you're looking at.
