Hang a plumbob on the inside of the outer wheel lip and one on the inner tub just in front or behind your axle, measure between the strings and deduct whatever you need for tire clearance and that will give you your tire carcass measurement and from there you can figure your wheel backspacing and what tire will work,do this with axle in the car, hope I explained that clear enough. Doug

I used this method on my Bbody as I ordered a S60 from Strange and had moved my springs in to the frame rails using Caltrac splits and I wanted a wheel that was an even split on the wheel front and backspacing and there was no extra charge to have it built to my measurement.