how big of a tire can i use with 17" rims?

[bigarmzz]

i know alot have asked similar questions....but i did a search and still couldnt find a direct answer.....i've got a 3/4 drop with front spindles and rear shackle/hangers.....i want the "muscle" look with lots of tread (meat) in the rear...ya know i just want the tire to fill in as much of the fender wells as possible

i was going to run 285 70-15 X8" torq thrust II's....but the cheapest i can find the 15" ones on the web is $690 and that just seems high for just 15" rims to me ...so i'm thinkin about spending just a few bucks more and getting the 17" rims, but i'm not sure what the equivalent to the 285 is in a 17"?