the question that comes to my head is, is it at top dead center on the intake stroke? that's what you need to do is turn the crank until it is, then try to insert the distributor. Maybe by chance when you put it in a tooth off, and took it out to fix it, maybe you went the wrong way?
when you figure that out then to get in the general area of the timing...
here's a pic of the position of the distributor in my car @ 10°
copy and paste:
www.angelfire.com/ma4/fromentlogic/
images/distributor.html