Probally a 285/40R17 but it really doesn't make sence because the tire won't contact the road right, resulting in improper tire wear, poor handling, and no extra traction. I would stick to 245' or maby a 255 series.
Rule of thumb - for good tread contact, section width (the first number in a tire size - 225, 255, etc.) shouldn't be any more than 2" wider than the rim width. That first number is in millimeters, so you have to convert to inches. Here's the math. 8" rim +2" = 10" section width. There are 25.4 mm/inch, so 10" = 254mm. Therefore, 255 section width is about as big as you should go with an 8" rim. 90Mustang's right on.