Lil ID help for a rookie

I"ve got a '73 swinger w/ a 318 I'm still familiarizing myself with. I'm hoping to get a little info from those out there who know. I pulled the old brittle build sheet from under the rear seat & I'm having a tough time breaking the codes. trying to ID what tranny, diff & gears I have.

build sheet codes:

Trans: 063
Axle: 973

Just from reading I'm guessing I'ts a 904 tranny with an 8.25" rear and couldn't know less about the stock gears.

thx for the help.