I am crying 'foul'.
The 1978 CB750A didn't come with the Akront rims, it came with Comstar wheels. The 1978 had dual exhaust (4 into 2). The 1978 had cast aluminum passenger foot peg mounts, not the steel frame extensions shown. Your pictured bike is a 1976 with Akront rims and stock four into one exhaust and stock passenger foot pegs (in other words a 1976 frame). The seat is not 1976 stock but it was available as a Honda option.
And we can't check eBay ads from 2006 (where your pic was taken from).
Here's a 1978 Honda CB750A that sold at an auction in Vegas January 2014, survivor with 4000 miles.
http://forum.motorcycle-usa.com/attach.aspx/3896/750aleft%20small.JPG
Here's a 1976 CB750A with the optional seat, (although the seat appears to have added padding).http://media-cache-ec0.pinimg.com/736x/08/75/6a/08756adcc3e671e8801653dd2168e16a.jpg