That is the difference. The offset is 5/16" different between the 2 blades. The 396-807 has the 5/16" offset like the newer 09081200 while the 396-740 blade has a zero offset. The 09081200 is the blade listed on the Gravely parts radar as the correct blade for the Pro Turn in question.
Hey, thanks again for a wealth of information. I love this site!