The floor in the 4000Q and the UR are very similar.
There are very few similarities between a coupe GT and a Quattro.
If you have a Quattro, mechanically nothing is the same on a coupe GT, not the motor, not the transmission, not the Diffs, not the drive shafts, not any of the suspension.
Body wise, the doors and hood are the same and some years the trunk lid ( after 1984/5 the Quattro got a composite lid). I guess the glass is the same. Interior wise, again not much is the same.
Really they are 2 different cars that look similar.
The Quattro was a hand build car produced on its own production line by a small team in low numbers. Pretty special, much under valued but starting to catch up.