If they had not played it safe and built Little Boy just in case implosion did not work, they could have made four implosion cores from Little Boy's uranium. That would have given us a total of six atomic bombs by the end of August.
Seven more bombs over the course of September and October and then five more bombs in November would have given us another twelve atomic bombs.
Kokura Arsenal and Niigata were still on the official atomic target list.
I personally think Yokosuka Arsenal could have used a good atomic bombing as well. That would have given the Emperor a nice view of a live mushroom cloud.
Ideally Truman would have overruled Stimson and had Kyoto on the atomic target list.
And ideally they would have kept Yokohama on the atomic target list so that it would never have been conventionally bombed. That as well would have given the Emperor a nice view of a live mushroom cloud.