Is it direct-mounted? Or on a pickup ring? Can you post a pic of the guitar?
If it's on a pickup ring, I'm almost sure it will fit unless the route is really shallow. The only time I had trouble fitting an 81TW in a guitar with pickup rings was in the neck position an Ibanez S, but you know how thin those bodies are and how shallow the routes must be to accomodate it and how you usually have to have the neck pickup lower than the bridge. Other than that, it fit in every other guitar with pickup rings I've tried to fit it in.
If it's direct-mounted, I have my doubts. The 89 is the standard pickup size for EMG's. The 81TW and the 57TW are taller/deepr. But even on direct mounts not meant for actives and the 89 which is standard depth, the quick connect terminal might get in the way.
