Make sure that you get some replacement copper plugs too, our host sells them as well.
I used some small set screws and little nuts, deffinantly not ideal. Next time I'm in my doors, I'll be replacing the screws with copper plugs.
While you're in there, replace the felt that the window slides through. Very ease to do espeically if you're going to pull the quarter panel anyway. You'll have to take at least pull some of the felt out of the way to replace the window block, might as well just replace it.
I posted a thread about this a while back, but I don't keep track of them like I should.
Here's a picture:
This is before I removed the quarter panel assembly. I didn't realize that the window guide rail would have to be removed to gain access to the channel block.
Here is a comparsion of the old block and the new one (before I installed it). You can also see the copper plugs that I dremeled out.
-Matt