seems that its the same width as the 1500 diff (which comes with alloy housing)

Bluebird axles will be a fair bit to wide, and will need to be cut down and resplined, but i dont know if they are wide enough to clear the undersized part
also the 720 and 1500 wheel bearing arrangement is much different to the normal passenger car wheel bearing arrangement. being that they use tapered bearings with adjustable preload all contained in a bolt on "hub" kinda thing
the axles are also threaded at the wheel bearing for the adjustable collar

so to use bluebird axles you would need to cut the ends off the diff and weld the bluebird style ends on to allow you to use bluebird wheel bearings. and if you were doing that its not much of an effort to cut the diff down to 1200 width

another option i was looking at if the axles werent going to be long enough to allow resplining was r31 axles. they are big enough to be resplined to the h190 spline even in the undersized part of the axle
but you still have the problem of the different wheel bearing setup on the 720 diff. so still need bluebird style ends and then you need to find a wheel bearing with bluebird bearing OD and r31 bearing ID, then same deal with the seal as bluebirds have it on the inside of the bearing and r31s have it on the outside

im wanting to go down this path for the 1200 wagon, bluebird h190 with alloy centre to shed some weight compared to the r31 diff i have now
but from looking at the 1500 diff it seemed easier to start with a bluebird diff and cut it down compared to making a ute diff work with 4 stud
but i also couldnt work with the increased track in a 1200 as the guards arent as forgiving as in a 120y

they are however a good "bolt in" diff if you dont mind the track increase and 6 stud