Just depends on what the Mustang calls for with the servos and whether or not the servos for the Stinson meet those specs? My suspicion is that those servos will be too small.

One of the downsides to going with bigger models is that the electronics get expensive real quick, but they're really the heart of the whole project and I find no reason to skimp on that stuff for that reason. As a rule of thumb on smaller models (once you get to the size I usually fly, you just get the biggest thing available... ) I like to pick a servo which exceeds the manufacturer's recommendation by 50%.