I'm close to that part of my project.
My research so far shows that at one point there was an opinion that you need to get Sti cables , for the parking brake to work.
There are 3 variables:
which year body and existing cables (they change with the introduction of the '05 console with 2 cupholders possibly the parking brake lever got moved forward and requires longer cables.
Which year parking brake handle are you going to use, some Sti may have a different and more rear mounted cable hookup
Which year parking cables you are going to use.
Oh, and from what I'm seeing incompatibility puts you out of adjustor range.
My simple answer will be to keep my cables and parking brake handle and cables and hope that they extend enough to reach with the rear Sti hubs, I'm hoping to use '04's
As far as the drum itself, once you do Sti hubs, you're on Sti rear brakes, so there's no unknown there.