Yes I noticed that too. He says he built another 727 for it. Also look at the pump..... It looks like a 727 pump and the Sun Shell looks HUGE compared to the 904......maybe its the picture.
That is definately a 727, Just looked up the sunshell on wittrans.com the 727 shell is not as deep as the 904 and the circumference is alot smaller. Also the 904 pump does not have that plastic vent/pickup on the pump that faces the inside of the trans.
One thing that threw me off is the pan rail on the trans. Looks like a 904. Did other years have a different pattern? Maybe that is the picture also. Looks like it is a 727 now that I looked at it harder?