File export wavefront object, click universe to clear hierarchy, select(x) each block you want to include, uncheck all export options except include existing groups in polygon groups. Export. Now, here's the thing... whatever transformations you have applied to the blocks in scale, translation and rotation will become the default state of the new single object. That is, it will be 1 object with a single center of rotation and its position and scale at the time of export will be a value 0/100% in the new state. You can disassemble the object into its constituent parts (because you exported with groups maintained) via the group editor by spawning props from groups, or materials.

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