Get a straight edge and a ruler or a tape measure lay the straight edge on the rim back side then use the tape and measure from the bolt flange to the straight edge and there's the back space.

 Ok thanks guys, makes sense, I will measure the backspace when I get home, not sure that it will change anything but I will know where I stand at least and know where I want to go from there. I do know however I dont really feel like  I want to spend a bunch of money on wheel/tires since these are in good shape right now, my focus is more on getting things on the road.

 Also Steve, you said you could have used a 1"spacer in leiu of "trimming" the backs of the rims, is there and disadvantage using spacing, could it weeaken the integrity of the mounting of the tire? Is there a maximum amount one could space a tire out?  Also, I would think if you spaced the front tires out, I would have to lengthen the tire studs to be able to fit, again is there any rule for maximum stud length? As I typed that it kind out came out sounding stupid, but oh well, just again resourcing options here.
Thanks

  Those look pretty nice, and substantial. I have spacers that just "slide" over the studs and are held in place by the rim being bolted on, and are maybe 1/4 -1/2 inch.
 
 I am trying to recall the tires sizes, I know for a fact because I just looked the other day that the rear tires are bigger than the front, I believe the tires on the back are 240  75  r17 (  the same size as my audi) and the front rubber is 220 40 r17, but I am not exactly sure, I am positive they are smaller just dont recall the exact size.

    I will have to install the brakes and see if I can make them work, but I would like to know definitively before I get there if it will work or not.
 

Those sound like 17x8 with 5.72" backspacing, same as mine from 01-04 Mustang.  A 1" spacer like the ones pictured will get them mounted, but you can expect some fender rub unless your car sits real high.