I have an old house with 4"x8"x16" cinder block exterior walls. The headers are the old precast cinder one piece units. The interior side of the block is 3/4" lumber glued and screwed to the block with drywall over top. I want to avoid modifying/touching the block. Years of poor repairs to the door frame have taken a toll on the block ends. I'm wanting to replace the door, and I also want to get some space for new electrical and insulation. I'm considering framing a 2"x6" wall on the interior side and moving the door to this new wall, resulting in a recessed doorway. I would remove the siding on the exterior and wrap the block ends with aluminum. This portion of the house is on a slab, and the existing door sits directly on the slab, so I would need to build a masonry "cant" onto the portion of slab left exposed from the recess. I'm a skilled tradesmen, but have never attempted this type of door modification task, any guidance would be appreciated.