Hi aaron,
It would be good to know.
I have a couple of Phase 1 AWDs.
Note that there are two versions of the centre bearing for those (1998 vs 1999). There is a difference in the spacing between the bolts that mount to the body. This should match the spacing on your car. Otherwise the shafts seem to be compatible between 1998 and 1999 but I haven't tried.
Looking at Phase 3, the other thing to check (as well as the length of the two prop shafts) would be the number of bolt holes in the CV joints and the outer diameter of the CV joints, to be sure that you can bolt it up to the flanges at the front and rear.
If you are thinking of changing the CV joints at some time, you would also want the number of splines and the diameter of the splined prop shaft ends to be the same. Presume also the spline profile.
I dont have a Phase 3 shaft so I can't comment on any differences.
If you look at specs from components from rebuilders such as
https://www.driveshaftparts.co.uk/ or
https://www.jandrcvjoints.co.uk/ you might be able to work out the differences. A rebuilder would be able to tell you pretty quickly.
HTH
Steve