My very strong suggestion is to stay as far away from VMAR products as you can. I purchased 3 now, a Chipmunk, a Harvard II and an Ugly Stick 60 size. All were manufactured very poorly. Materials, craftmanship and assembly instructions the worst I have seen and I have flown & built many ARF's.
All of these planes ended up in the trash bin after one or two flights. There have been several threads on this forum concerning VMAR products and the consensus generally has been the same.....substandard!!!
If you are looking for a perky, well manufactured and beautiful-looking and flying Mustang, I would recommend the World Model's 40 size P-51D (The Flying Undertaker). It comes with pre-installed retracts and I have powered mine with an OS 50 SX with a Bisson muffler. I have over 30 flights with this plane and it performs very well.
A word of caution...this plane is not for the beginner! No warbirds, especially Spits & Mustangs are really. You should be comfortable with taildraggers and very responsive low-wing aircraft before flying one of these. When you are, then a straffing run down the runnway with the gear retracted, followed by a victory roll or two, will give you goose bumps!
I have included a picture of mine.
Good luck!
-Paul