furnaceman called it right. If you are going to buy the P51 PTS as you stated, it does not have retracts. It comes with fixed landing gear & an optional flaps that you can either hook up a servo to & use it as a functioning flap system, ot you may choose just to set it at one of 2 fixed positions.

As nice as retracts are to have when working right, they seem to be the Aquiles Heel of every Warbird. Even the good ones. I just watched a set of $200 Robart Air Retracts fail today just like the mechanical ones that they had replaced. I see it every week at least once if not several times.