I have a 180 and four 120's, but not a 150. Alas, my buddy moved out of state about 4 years ago and have since not had much contact. But a 150 should be real close to a 120 in physical size. The 180 is not that much bigger than a 120 as far as length and mounting holes go. Naturally head height would be somewhat taller, but just a little. Grupner props can be had from here http://www.hobby-lobby.com/grprop.htm
I prefer them because of looks mostly, they have a good scale look about them and it worked fine on a 150 and a 180. Here's a pointer to some dimensions. http://www.horizonhobby.com/ProdInfo...der_Manual.pdf You can find saitos manuals on the horizon hobby web site. Look under the support tab for the engine and there will be a link to the manual. This manual covers the 120, 150, and 180.
I dont know about using metal. I know some people that had real good luck using Behr latex house paint in silver. Looked pretty good, I'm going to try it on my P-47 when its time.
Edwin