'65 Formula S with "factory" 727 and 8 3/4?

I have a '66 V-100 with an 8 3/4 3.91 SG that looks to have been there from day one. The build code for the axle is 173,I can't find a reference for that # in the white book,but the 41 code for the pinion would seem to be correct for the ratio. I will start a new thread on this car & ask for help decoding the broadcast sheet.