what later model steel wheels can I use on my 51 Chevy 2dr.sedan that would still be 15x5-4.75 bolt pattern and clear disc brake calipers?Also I would need at least 3 5/8 backspace.

Check with Stockton Wheel they should be able to set you up. Here's the link;

http://www.stocktonwheel.com/

Larry

I think 80s Camero will work etc.

Good luck.