I am buying a set of 15" American Racing Ansen Sprint wheels for my 1955 Thunderbird and am looking for some input.  I'm not exactly sure how to measure wheels.  My stock steel wheels look to be 5" wide between the mounting flanges with a 3 1/2" backspacing.  I assume this is what came on the car?   The car looks and drives great with these wheels and 215-70R15 tires.   I am not running skirts on the rear.  My car currently has drum brakes. 

The narrowest 15" Ansen Sprint wheels I can find are 7" wide.  They are available with 4" backspacing.  Is anyone running 15" custom wheels on a '55 Bird?  What backspacing do you have?  Thanks!