Dave,
The Ryobi 31 and the Homelite are the two common conversion engines in the USA. Most reed valve singles have the carb in the rear, such as ZDZ, 3W and DA. Go to wackerengines.com for pictures and parts. Checkout this website on Ryobi conversion. It is old, but will answer some of your questions. Also vist the engine conversion forum on RCU.

http://www.geocities.com/CapeCanaver...216/webww.html

Dave