I know this thread is a touch old, but just in case the OP is still around...
I used Amphigory's Pure in #1B for Mustang:
In hindsight, it is
a bit long, and I had to trim the sides. If you're wary about cutting, I would also suggest the Young:
Or also New Look's Edward. I got the Edward for King Bradley, but it probably would have been a good style for Mustang. Like the Young, the Edward is lightly layered so you wouldn't have to do it yourself. Happy hunting!