Backspacing wheels

[Blue72]

so apparently a WJ has 6.5" on standard 17" wheels.
If I was looking at firstly 245/70 R17 tyres I dont need to do anything,
but if I was looking at replacment wheels eg a nice set of Mickey Thomsons or something, what do I need to look for.
So same stud pattern but if they say 4.5 sapcing, does this mean I need to space them out by another 2" to fit the same as the standard??

Its seems so confusing!!!!!
or does this only really apply when fitting big wide tyres???

Found a link that helps a little but really need your guys advice!!
cheers
http://www.wjjeeps.com/wheels.htm

I have the silver blade fitted
Andy

[Dave69]

you dont want to add 2" spacers to the wheel hub as this will put the wheel further out of the arch and it will add more strain onto the wheel hub etc. with the wheel rim taking the 2" in the change of backspacing will keep the wheel sitting better in the arch and reduce the strain on the hub etc