ok, heads spinning, just need a straight answer...

found a set of 18 x 10 inch rims but the back spacing is 6.38 :-(

damnit...

That could work. Have you done any measuring? If you don't measure your car up, it's very hard to get a feel of what wheel offset could fit.

I would measure that 8.25" rear. It's probably not wide enough for those rims to work without a spacer, but it may be close enouch to use a set of spacers. My 18x10's have a 7" backspace and work fine with my B-body 8 3/4. It's all about the width of the rear axle.