For LA engine work, the oldest manual I'm aware of you can download is a 66, but even the 68--72 manuals are OK for much of the drive train
66 manual from MyMopar. You have to "play" with page numbers
http://www.mymopar.com/index.php?pid=31
download link:
http://www.mymopar.com/downloads/servicemanuals/1966_Plymouth_Service_Manual.zip
69 Dart manual, again, much of the engine/ trans stuff is the same. These use the "normal" Chrysler "dash" page numbers
http://www.abodyjoe.com/pictures/Misc. car info/69 dodge service manual.pdf
