I am currently working on a 1945 and will share with you what I have found.
Your serial number will come in handy here. 223151 and above is the &quot;three gear engine&quot;. Below is what is called the &quot;five gear&quot; engine.
There have been a bunch of what Oliver called field upgrades. Like Ridemaster seat and distributor as opposed to magneto in the &quot;70&quot; history.
Mine is a distributor. 
I suggest contacting the Floyd County Museum in Charles City, Iowa and purchasing a shop manual. I am sure it will prove invaluable as would an operators manual. The operators has a wiring diagram but is not as in depth as the shop.
I hope this helps.