What is the original application of these two bellhousings? Both are B-O-P. They look identical and have the dual Muncie/dearborn (FoMoCo) 3&4-spd bolt patterns. There has to be a difference, right?

There's a reproduction of the 9778882 & the parts books I have all show the 9785581???

 

Anyone? Anyone have a ''64/'65/'66 parts book? What's it show? SECTION 0.683

 

Any chance one is for a Starfire?