I just put a mk5 rack and a RST rack side by side yesterday and made the following observations:

The threads for the rod ends are coarser on the mk5.
The rack is of similar length from inner joint to inner joint.
The mk5 rack is ~10cm longer from the end of rod end thread to the other end.
The valve assembly is surprisingly compact in the mk5 rack which is nice.
The take off for the steering axle is a good ~6cm more to the center line of the car.
The diameter and number of splines is totally different in the mk5 rack's steering axle take off.
The angle of the take off was the same.
The mounting to bulkhead would need a simple adapter assembly.


Still the best rack I have seen is the Nissan Bluebird rack. It's also only 2.5 turns end to end. The mk5 was over 3.