Test if there is a game object at a certain position

I am making a runtime 3D generator, when the blocks generate, i have some blocks at the same position as another block. How do I see if there is already a block there, so unity knows that it should not generate a block there, but somewhere else. I already tried Physics.OverlapSphere, but that returns the collider information, and all i need is a bool. Anyone know how to do this?
Thanks in advance.

If you only want a boolean, use Physics.CheckSphere().