There are two main "hard points" in rear wheel placement in the rear wheel house. One is the pinchweld where the wheel house and the outer quarter panel skin come together. The other one is the rear leaf spring/inner tire sidewall area. You'll need clearance at both places to allow for bushing deflection under cornering loads. With the common mounbting point being the rear axle shaft flange.
There can also be a related clearance dimension between the rear brake drum and the quarter panel area, too. Might need to take the rear shocks loose, letting the springs completely support the rar axle (with the car on a lift or secure jackstands). Might not be quite so close on your car as the OEM 14x6.5 wheels with P245/70Rx14 Advantage T/As are on my '67 Newport, which took a bit of effort to find the right angle between the tire and brake drum to get installed (with 11x2.5 rear drums).
Just my experiences,
CBODY67