On an undamaged original, there are also 1 or 2 nuts stabilizing the unit on a side bracket.
The bracket is bolted to one of the exhaust manifold studs, but you just leave that part in place and remove the two nuts, pull the bracket to the side slightly and lift the housing upward as James described.
By now many of them have broken off either at the exhaust manifold end, or have come un-glued (welds broke) from the side of the air cleaner housing.
If yours is intact, good on you and the PO's for keeping it in such good shape!
Paul