1957 62 Series Wheels

[Dave]

I am preparing to purchase new wheels and tires for my 62 Series car.  I have measured my current wheels and get the following numbers (approximate).

15X6 wheels
5 bolt circle
4 backspace
0.6 positive offset

I have looked in my service, authenticity, and parts manuals along with numberous links to websites to verify the correct specifications for the wheels with no luck.  Can anyone verify the specifications for the 1957 62 Series wheels or point me to a source of information?  I am particularly interested in verifying the backspace and or offset figures.

Thanks,
Dave