alternator removal

I am having a hard time removing the alt from my 90 Colt HB with a 1.5L. The top bolt and the elctrical connections came off quite easily but the lower bolt is giving me a headache. I took the not off of the back side (towards the pass side), but the bolt will not come out. Is there any trick to it? The head of the bolt on the drivers side is square and sits against a boss on the alt. to keep it from turning. What is the deal with it?