After continual problems getting spinners to fit and keeping track of back plates, spacers, and so on, I just decided to go with an aluminum prop nut.

http://www2.towerhobbies.com/cgi-bin...&I=LXE158&P=ML

You can use the flywheel if you like, but the prop nut of the right thread size, 1/4 - 28 thread, will fit any engine with the 1/4 - 28 thread. They even come in brass to add weight in the nose if you need it.