Checked out that site. It also came back with the OS as 12617631.
Of course I see it was my mistake. The ECM shows 12617630 but the tune file does have the OS as 12617631 (12617630 is the calibration).
I can get the 12612384 / 12617630 ECM for $40 (who know what OS is on it) or 12612384 / 12617630 ECM that is reported to be from the 2008 truck for $100. Guess I'm better off with the $100 ECM.
Thanks!
Rob