Online Community of Zenith Builders and Flyers
Go to this website http://www.newplane.com/ that provides documents for the defunct AMD line of factory built Zenith aircraft. On the top left corner click on "continued airworthiness of factory built CH designs" and then scroll down to the AMD 601XL section. You can click on and get a Pilots Operating Handbook, a Maintenance Manual and a preflight checklist document that is very extensive. The AMD version had a Continental O-200 but that makes it very similar to a Corvair, operationally. You should be able to use much of what you find there to write your own manual from.
Another manual you could borrow ideas from is the one for this Corvair powered plane.... http://www.zenith.aero/forum/topics/excellent-601xlb-td-for-sale In the text of the For Sale listing he gives a website link for data on the plane. Most of the way down that extra data there is a link to look at his Pilot Operating Handbook as a PDF file, and his Handbook is written specifically for his version of a Corvair powered 601XLB. Again, you could not use it verbatim but there are a lot of good ideas there to "borrow" for your manual and checklists.
My plane is not yet built but I have copied both those manuals and I plan to borrow from them heavily when I write my manual for my plane.