Guys, I bought a pre-ban Colt Sporter rifle, lower is stamped 9mm, has the raised fence, sear block and the three holes in the magazine well. It also has a large front pivot pin - someone told me it has been drilled out. How can I tell? Is there such a thing as a Sporter raised fence with a large hole? Is there a Colt 9mm upper out there with a large hole?
Thanks, I'm trying to decide what to do with this.

You bought it as a complete lower only?  Was the blocks installed in the mag well?  The holes in the mag well are/were to hold factory installed blocks convert the 223 to 9mm.  If the mag well will accept a 223 mag, then someone took out the 9mm blocks.

I can't say about the large hole pivot pin.  I'm not well versed on the small hole/large hold thing.  It's possible.  But using one of those hole/offset adapter will solve any problems of putting a small hole upper on it.