Tires and rims

I have a 1986 Chevy Monte Carlo SS stock suspension.I got hold of some free M/T Et street radials the size are 325/50/15. My question is what size rim and backspacing do i need to make fit?I know they will stick out some from under wheel well.Motor putting out around 500hp maybe a little more was told they were to much and will bogg out its a street car.Also rear end is a 7.5 10 bolt was told just change the axles and it will be fine on the street. Someone help me out please!  

I'n not sure about your backspacing or rim size, that will fit under the Monte.,. someone in the know will chime in soon enuff.
The weak link of the 10 bolt are the spider gears, cuz they'll cut loose before the axles will.,. you can get after market "C" clip eliminators, which is a step in the right direction for modding the rear end.

 
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P. Engineer.,. Engine Builder

obviously the width of the tire is the problem,A 9" rim is a must for that size tire and it would require a 4 to 4.5 backspacing to come close,that will be a tough find in a 15" rim there are lots of shops that can slightly swell the wheelwell area and or roll the fender lip,then you might get a 10" rim but they are usally a 4" backspace you really do not want to Jack up the rear of the car to clear the tires,some where some how the body will hit the tire,not to mention how it affects the handling.do not forget this...Any thing you do to a car changes something else and that also needs tending to.It's a system not a part.