7 1/4 axle shafts needed...

73 up 7.25's, at least if they are from a V-8 car are BBP. I believe you will also have to go with a 10" brake set up, as the BBP axles
won't work with 9" brakes.
Yes the rear I have is out of a 318 Brougham and yes it has 10” brakes.