Inliners International Forums General Discussion Engines 235 six horse power rating

Good morning,
While looking at the various specs on a 235 chevy six motor, I see that the horse power rating on the 235 stick is 123 HP... The Power Glide is 136 hp.. Both enigenes have the same bore and stroke and run a single barrel Carb.
Where does the addtional horse power come from between the stick and the Automatic.
Thanks
Mike