Just wanted to share my experience with aero-stuff.com. I bought the direct drive manual and parts manual for my IO-540 for $27. It was delivered as a downloadable PDF file and the quality is great.
Also found this site which has some manuals for free downloadable (http://pj260.com/Lycoming/)
Also found this site which has some manuals for free downloadable (http://pj260.com/Lycoming/)