I don't know what brand of spinner you have, but my Tru Turn spinner had to have the backplate reamed to .394 inches. Depending on the prop, it may have to be reamed also. Trying to drill it might not be the best answer, as a drill might not get the hole dead center. You can imagine what the vibration levels will be like if its slightly off center. Either ream it, or use a lathe to bore it. The same holds for the prop and washer.
Hopefully someone in your local club has the tools to do it. A machine shop would charge a pretty high price to do the work.
Good luck with it.