9in help

Hey all.
Found a speedway fabricated ford 9 in for a good price I might not be able to turn away. The car I’m looking to
Put it into as a 73 swinger. The model of the axle is the 56in version as show in this link.

Speedway Ford 9 Inch Rear End Housing Kit with Axles, 56 Inch

Being that I’m not sure on how the 9 inch goes together with axles and brakes I’m not sure around how wide the finished 9 In rear would be. I know the factory 8 3/4 is around 57 inches drum to drum. But is that front of drum or rear of drum. Just trying to see if someone with experience on this would be able to let me know
If this rear would be way to wide fully assembled or if I could make it work.
Thanks a lot !