RE: 3 blade or 4 blade prop for TF p-51
Four blade P-51 spinners are available from Tru-Turn and others.
One problem is that a prop that is the right size to be scale is going to be too big for the engine. Jacked69 has a Saito 1.00 on his model. According to the product description, the plane is a 1/7 scale P-51D. The full scale P-51D used a 4 blade 11'2" prop. A 1/7 scale prop would be about 19 inches. That would be a really big prop for the Saito.
The other problem is that very few 4 blade props are available. Using the 'load' numbers from ThrustHP A 14X8 2 blade is fairly equivalent to the following in a 4 blade
14x4
13x5
12x7
11.75x8