My first conversion was a Featherlite Blower, just finished this weekend
$70 from [link=http://www.lowes.com/lkn?action=productDetail&productId=90618-000000283-FL1500]Lowes[/link]

Really easy to do. Ran for 30 minutes as a blower. Pulled everything off the motor. Trimmed off excess aluminium with a RotoZip. Trimmed and balanced flywheel. Added a hub. Trim crankcase backplate on bandsaw. Made a motor mount out of HDPE cutting board. Cut the plastic throttle arm off carb and added a control arm. Cut a couple of 1/2" holes in muffler to open up exhaust. Mounted on a test stand. Wired kill switch. Used tank from blower. Started right up with $20 Tower starter

Couple of things, though. I'm using a carb off of a Featherlite string trimmer (the pics show two different carbs) because I couldn't turn the needle valves and I couldn't find my Dremel to slot them. Plus there is no idle stop (not a problem once mounted in a plane with a servo to control the idle.)
Also, this is a long shaft model, so the hub needs a 5/16" straight hole (instead of threaded)
The muffler is bolted on (unlike earlier models) but it has a 4 hole backplate which makes mounting easy (unlike later Featherlite Extreme models)

BTW the Lowes ad says 18cc, the box says 23 cc, and the engine plate says 25cc, so who knows

Turns 7400 rpm with a Zinger 15x8, Idles all day, surprisingly smooth, transitions nicely, hand starts with one flick when warm, have about 1 hour run time
Total weight is 3 1/2 lbs.
Going to try a APC 14x8 in am

Overall, I'm pleased for $80 and 2-3 hours invested for first gas engine. It's going in a 72" 1000 sq. in SPAD, projected weight 10#

Pete Johnson