First off, make sure the opening in the manifold is totally clean and FLAT, and the choke well is clean. You may need to file or sand. Next, try making a gasket with high-temp (grey) gasket paper. If everything is clean and flat, that should be plenty (that's how it came from the factory). If you must put schmutz on it Permatex Ultra Copper is your best bet.
If you want to try to go without a gasket, and just glue/seal the choke well into the manifold, use "muffler paste". Make sure each piece is sanded totally clean first, and hope you don't need to get it apart again down the road.