This thread reminds me of one started a few months ago about our responsibilities to others.
There is a some amount of planning and problem solving ability required in racing if you want to experience any degree of success. Maybe even if you want to do it at all.
The nature of these questions leads me to wonder: Are you a member of SCCA? Do you have an SCCA racing license? If not, do you know how to get to that point? If you are, how could you not know what a GCR is?
What you may need is a plan. It is great to be able to ask people that you know and trust for advice, but do you really know and trust anyone on a forum?
You should, at the least, supplement the answers you get here with your own research.
If you obtain an older version of the GCR there could be some significant changes to the rules depending on the year and the car.