It's a different part number (B6S-3504-A) and the S in the prefix indicates Thunderbird. I believe it is constructed differently and has different mountings than a passenger car but all I have to go by is the illustrations in the parts book.
The main difference between the FORD and BIRD is the input (steering) shaft and worm gear. Most everything can be interchanged. Another caveat (Fr.) is there was a design change during the 56 model run, the early box being a 2T sector gear and later a 3T sector gear, so you would have to ID which you have.