Backspacing or offset for '69 Mustang/Cougar

[F23]

Hi guys,
Does anyone know what backspacing or offset I would need to run on a 17x9.5 rim with normal sized tires? I Have a completely stock rear end '69 Cougar, which for this purpose is identical with a Mustang.

Thank guys,

F23

[latoracing]

Most people I've heard of using that size rim run a 5.5" back spacing with a 275-40-17. Haven't looked at a Cougar wheel well in a long time, but several people (on Mustangs) are running a 10" rim (6" back space) with a 295. Some clearance needs to be added to the front inner wheel house, and trimming the bump stop wouldn't hurt either. Check your opening lip to see if there is any interference with the tire, rolling might be in order to keep your tires in good shape.

Measure your car before ordering anything!