How to Remove IWC latch

As you said, this lock is no longer made. I would suggest considering our 90-313 as a substitute. You would need to remount the holes at the top, but it may possible work. I recommend a screw similar to the 33-011. You don't want to use too long of a screw, or drill too deep, as there is a risk of damaging the frame or the glass in the sash.

As for removing the old lock, I'm actually not sure. I've never personally dealt with these since they aren't made. Based on what I've experienced with similarly designed parts, the top part of this lock may be a cover that snaps on. See if it pops off, there may be screw holes underneath.