Easiest way to tell a reverse rotation engine if it's assembled is that it has an extension under the distributor. This is to take up thrust on the dist. gear, which would otherwise be transferred to the distributor

Like this

http://www.marineengine.com/boat-forum/attachment.php?attachmentid=6443&d=1363733766

annudder

http://i849.photobucket.com/albums/ab52/...Photos00000.jpg