Ok. I have the "cube-to-sphere" with quad-tree detailing. I have a height map that I use to push out the verts that I generate. From there I want to start generating the high detail with marching cubes. In order to use them, I need to have box volumes. The "cube-to-sphere" gives me an irregular grid pattern once put into the sphere, so I can't use that. However, before performing the "sperification", the verts form a nice regular grid pattern on the six faces of the cube. I think if I come up with a method to generate the marching cube voxels along the regular grid pattern (on the faces within range of the detail center), and then "sperify" those verts, they will still line up and look mostly normal. By mostly normal, I mean that there will be some "bunching" at the corners/edges where the cube faces meet. The bunching shouldn't cause any overlaps or gaps, though.
This doesn't seem like it will work. "Spherifying" the vertices of the cube is done by normalizing the coordinates, after which they lie upon the surface of the sphere. Then they are given shape by pushing them out with a heightmap. The spherification comes first, then the shape is applied. But if you generate a marching cubes volume first and then perform the "spherification" afterward the result will be a very messy yet smooth sphere of points. All the vertices of the mesh will be collapsed onto the surface of the sphere, and the shape will be lost with no real way to get it back.
Your mistake lies in thinking that you can somehow use the spherified mesh structure to do the marching cubes. You really can't, not in any way that makes sense, at least to my understanding. They are two completely different techniques. The sphereified mesh is a simplification; basically a hack to make a spherical heightmap. Heightmaps and isosurfaces are two completely different things, handled and created differently, and your best option is to go with the sphere technique from afar then use shader tricks to gradually blend in the volumetric mesh as you draw nearer.