e-Bay has Cessna 337 Parts & Service Manuals
 

There are both 337G and Pressurized 337 Cessna Parts and/or Service manuals listed on e-Bay presently... one auction closes in 16-hours, so better hurry. Also saw manuals for 1971 Skymaster. These are pretty spendy from Cessna, and the $49 beginning price isn't too bad, plus it doesn't look like but one person is bidding.

SkyKing