http://www.quicksilverdiecast.com/catalog/rcicd11.jpg
The A casting front axle was the first production starting in 1989 and soon changed to increase the strength of the front axle suspension. The A cast angular axle support struts are THIN and FLAT.
http://www.quicksilverdiecast.com/catalog/rcicd12.jpg
The B casting front axle was done to increase the strength of the front axle suspension. The B cast angular axle support struts are THICK and Flush with center chassis and angle outward to tires.

I know there isn't much interest in Racing Champions Indy cars, but hey someone may find this useful....