New 3 point seat belts

I borrowed one of the photos from moparmat2000 thread (hope that's ok). I want mount my upper mount just above and forward of the rear window handle so the belt and lower mount farter back (I'll try to do a line over this on the computer to make it more clear) does not show through the window. Has anyone done that type of install? Similar to what a covert may have had in the 70's. One thing I noted in Moparmat2000's thread was making the seat back latch. Need to do that on mine too.