brake lines

A ‘73 kit will have lines for an 8 1/4 rear axle, which has a narrower housing than an 8 3/4. So the lines on the rear axle would be too short.

It’s also unlikely the T/axle vent is in the same place, so the length of the lines on the axle might not be split to put the T in the right spot either. Even if they wouldn’t be too short to begin with.

You’ll need to piece your “kit” together, the lines on the axle have to be for model year A-body 8 3/4 you have (vent location moved at some point), front lines will have to be for ‘73 up disk brakes and combination valve etc…