can someone explain to me the difference between the different codes for the rallye wheels
thanks

Dont know quite what you mean but I'll take a shot at it.
All wheels have a one or two letter code stamped in them. This code can be found next to the valve stem hole(where there is also a date code stamped), or at one place between the lug holes and also stamped on a place on the interior of the rim. This code corresponds to the rim size and width and the vehicle it came from. Many rallye wheels of the same code and were used on all Chevrolet applications, while others only came on a specific model. So I guess if you find a wheel's code, you should be able to find out what it's application was.

Hope this helps