Go to your local library's reference section and see if they have a Hollander's Parts Interchange Manual. That will tell you if they are interchangeable provide it covers both years. As far as whether it is a 9 inch or not, can't help you there, but there is plenty of info on how to ID them on the web.
If it is a true 9'' then all you need is the center section, more importantly is pulling the axle and checking the spline count, ie if it is a 28 and yours is a 28 then the center section will fit, but if your galaxie is a 31 and it is a 28, then you are out of luck.
It won't fit without a few mods, and how to tell if you got a 9" is with a camera.
Or get a 9/16" socket and 6" extension, if the socket fits' the bottom bolt on the Housing then it's NOT a 9" if it will NOT fit on the bolt then it IS a 9" If the rear housing has bolts in it then it's NOT a ford rear at all....
what he is says is the 9" case overhangs one of the bottom bolts and blocks a socket from getting on it. The only way to remove the bolt is with an plain ol open end or box end wrench. If you cannot get a socket and extention on one of the bottom bolts (think it is the driver side one) then IT IS a 9" rearend.
All you really need is the center section but make sure it matches your existing 28 or 31 spline axles. You need to know what you have first. Also you might get lucky and get a 3.89 or something. But I would imagine it will be a 3.00 or something like that. My first 9" I got when I built the bucket was a 76 Cougar but a 3.00 open and 28 spline.