Generic wheel size

Hey Guys.

I have a 09 Tacoma TRD double cab off road 4X4. Part of the purchase negotiations was for them to swap out the semi-off road tires for Micheline street tires and me keeping the the original tires. My thinking was that when I did my 2% light off roading I could mount the original tires on some cheap steel rims and put them on the truck as needed. I wrote to Toyota for the bolt spacing, off set and center hole size. They won't tell me. I went to a junk yard and they laughed me out of the building. I posted an inquiry on a generic junk yard look up and got tons on junk mail. Some called and hang up when I told them what I'm looking for.
Again I'm looking for some cheap steel wheels. There seems to be something special about the 09 wheels.

Questions:
What is so special about my Tacoma wheels?
What is the wheels specification so I can search by spec instead of model?

 

6 on 5.5, 4.5 offset, 0mm backspacing, but it can vary from that a little. I wouldn't suggest the stock tires for offroading that much, but since you do it very occasionally it shouldn't be to bad.