I never did a Toro, but it should be similar to a Ryobi. First you strip off all the weedwacker stuff. You shouldn't have to change the carb, if you do it's probably not worth the effort, you just want to get do to as close to a model airplane engine look as you can. It probably has a magneto, and a pick up coil on the front, most guys turn the extra fins on the mag off in a lathe, then make a prop drive that fits over the end of the crankshaft so you can mount the prop. You might have to buy an after market muffler, but try to use the stock one.

I've converted 3 Ryobi motors, the first I used the mag, the next two I added IE, you want the IE, for $100 I have a 31cc motor that turns a MA 16x10 7300 rpm, idles at 1600rpm, hand flip starts.

2 Ryobi power heads for $13.50 each off eBay, and IE for $85.00 from http://lsproengines.com/lspro_012.htm