The standard kit from CH includes the ignition module(non auto advance), prop adapter, pickup and instructions...no machining at all. You just need to know if you have a long shaft, short shaft, or the key way is in the shaft or cast into the flywheel.
The pickup and the adapter are marked and you just line up the marks and you're just about their, a 'lil' tweaking is all you need to have it just right..I set mine with the degree wheel that comes with the kit, motor didn't like it and had to reset it at the field. Loosen the hose clamp and rotate the pickup a few degrees and it was their..
You will need to buy a switch, battery pack, and a plug to solder on the battery lead for the module...Terry will be glad to sell you these also..

Whacker Engines in Fla. makes a kit for the motor mount that is the most complete I've seen... $18.00 plus shipping..includes bolts, mount, carb spacer and new gaskets..He's just started advertising on RCU or he can be found on E-Bay if you do a search for Ryobi.

I have a 31 on a 8' wingspans Big Eliminator with CH ignition, stock steel muffler, won't hover, but will do everything else

Terry is a hoot to deal with..

My 2 cents worth..