2 different faces into just a single face

Hi, i made a boolean union between these 2 solids. But, actually, what i was looking for whit the boolean union was that the faces from the 2 solids that are next to each other, became a single face. Please, see the pictures i uploaded
This one below shows the 2 differente objetcs that were affected by a boolean union

But in fact, i want to get to this

If the faces are truly coplanar, _MergeAllCoplanarFaces should work to do that.