could I use this to run the rope through...
could I use this to run the rope through on top roping, replacing the pulley.
I'm not sure what you mean by "replacing the pulley" typically, in outdoor toprope operations, the rope runs through two opposite and opposed locking carabiners, not a pulley.
Therefore, a pair of these would work for the masterpoint of your toprope anchor, although they would not be optimal for a few reasons
1) The Attache is not as strong as many other locking carabiners, because its wide pear shaped basked does not align the load directly across the spine.
2) It's much more expensive than many locking carabiners
3) It's anodized coating will come off on your rope
The Attache is designed to be used primarily as a belay biner, and for that purpose it is the best in it's class. Its round stock, perfect size, red "danger" stripe and keylock make it smooth and easy to use.
For a toprope masterpoint (and general use actually), I'd recommend the Camp Orbit in "polished". Not only are they light and cheap (2 for about the price of one Attache), but they also have a keylock and won't blacken your rope.
If you are going to be toproping exclusively, frequently, and at crags with very short approaches, you could get a pair of steel carabiners. Although quite expensive and heavy, they are disgustingly strong and realistically will never wear out. Backcountry.com only carries Omega Pacific's Steel D.