You can join Mustang club of America and qualify.
I didn't tell anyone this, but if you do a search for Mustang Club of America X plan number, you can find the code needed to enter the site and get the price.
You are supposed to show your membership card when you buy, but my dealer has never asked. On a Mustang, if memory serves me, you get about $1500 off the price and you still get to keep all rebates. You may get a bit less for a trade since the dealer is limited as to how much profit he can make from sales of a new car on an X plan. He might try to make that up by getting your trade cheaper.
I have bought many cars on X plan with no problem.