As a third plane, I would still stay away from warbirds. Go with an advanced aerobatic palne (Twist, Uproar, Tiger II, Four Star 40, etc..) Warbirds sometimes have nasty characteristics that can bite you hard. Snap-stalli (or sometimes tip stalls), higher stall speeds (especially during landings), longer take off rolls, not as forgiving in flight. Experience is the key to being able to fly a warbird, if you don't have a lot of it under your belt, stay away. That shiny P-51 in the window is pretty to look at, but unless you want to bring it home from the field in a bag, get lots of flight time first.