65 A Body wheel clearance

[1LIVEF85]

So I am trying to fit 2002 Pontiac WS6 wheels on my 65 Cutlass. I have been
surfing n lookin for hard #'s on what stock backspacing is for these rims,
some say 6" some say 7". I put a paint stick across the back of the rim(sitting on tire)
n I measured more like 7.5". I tried to bolt them up n the upper ball joint up front hit
n the inner frame/wheel well rubbed in rear. So I have a figment problem.




So my question is, how much clearance do I need n how thick of a spacer should I buy?

I have been eyeballing a pair from cal-customs for $93 @ 1.25" thick. Would that be thick enough?
Oh n the tire size is 275/45ZR17