WR 18" rear wheel fir on a YZ 250

[little jeff]

I have a '05 YZ 250 with the 19" rear wheel. I want to convert over to a 18" rear wheel. I have found to do this is kind of spendy, I knew from the beginning it would be. I was just wondering if an '05 WR 18" rear wheel would fit on my "05 YZ 250, and would the sprockets be the same as far as hole patterns and would the rear brake rotor still fit the YZ configuration? I'm just trying to save a few bucks here.
Any input would be appreciated.
Little Jeff