THANK YOU for digging that up! I really appreciate it!
In my case, the air filter element fit perfectly on the raised base of the oil bath main housing once I took out the oil pan (for lack of a better word). I think it was an 8" or 9". I got it through Summit, but Im sure Jegs has it as well.
The latest mod I did to it was to get a 1/4-20 coupler nut to put on top of the chrome lid. I then got a wingnut with the threaded part attached (found it at the local hardware store and looks like the OEM wingnut). I use the threaded coupler nut to hold the chrome lid on, then just screw the wingnut with the shaft into the top of the threaded coupler to hold the "oil bath" lid on.
Hope this makes sense; let me know if you need more info.
Ron GroveWauconda, IL