Hello Gravityisnotmyfriend,
To answer your questions. Mine has a single pinned ring. You can use a feeler gauge blade of about .008 or so to ease rings out of the grove without breaking them. You don't have to thread the shaft. Use the parts that came with the blower or der some with the rings, if you don't have them. The hub that went into the blower impeller should make a nice prop driver. I am attaching a few pictures that I just took of mine to show how it should look. The hex section that is inserted into the impeller will be cut off with a hack saw and carefully filed flat. This will make an engine with a very long shaft and will fit nicely into a streramlined cowl, such as my Goldberg Ulimate. The engine turn counter clockwise when viewed from the flywheel end. The case and back plate must be trimmed to save weight and provide a flat surface for the mounting plate. I weightd the parts and it should weight about 57 oz. mounted less prop. The long shaft will also move the engine back for easier balancing.

Dave