We have the two dealers with the highest allocation, both over 1,000 Corvettes a year as our forum dealership supporting vendors. Both MacMulkin and Kerbeck are an excellent place from which to buy your 2015 Corvette. When Chevrolet allocates Corvettes, they do not add multiple dealerships owned by the same company in determining which dealer to reward, so even if we were to know the totality of Auto-nation's Corvette allocations for all of its dealerships combined, it will not be useful information, not help if you are trying to get a constrained Corvettes. We do not have the specific allocation for individual Auto-nation dealerships, other than the one listed below.
This is the only information we have that might be useful to you. Notice that there is not an Auto-nation dealer even in the top 50 dealerships on this list.
If you are looking for either a Z-51 or a Z06, the following two threads will be useful for you. Good luck, and paraphrasing was is often said, "choose your dealership wisely."
If you are specifically looking to order a Z-51 StingRay, please read this thread.
If you are looking to order a Z06, and haven't seen this thread, it will be useful.
Bottom line, as you know, if you are wanting a constrained 2015 Corvette, please keep doing your research to insure you get what you want, when you want it.