The new design is strictly related to the "swing arms" themselves, the brush guard portions of the bumpers remain the same round tubing so front and rear bumpers match, even if you already have one of the bumpers installed. The square tube swing arms are for both driver and passenger side. The square tubing swing arms has been used on the Sprinter Aluminess bumpers for a number of years, so reliability and robustness has been proven.
The spare tire mounting system changes quite a bit. It is now a modular unit which bolts to the new square tube swing arm vs the older design which had the mounting boss welded to the round tubing. The need to define 8x6.5 or 8x170 lug pattern is no longer a requirement because the spare mounts with two studs instead of three. What can be important is specifying the thread pitch of the studs if you want them to match the lug studs on the axle hubs. One of the studs is pressed into the mounting plate, the other stud can be positioned for different size tires (31/33/35) so the tire clears the door and the tail light.
What the new square tubing design allows for is the ability to mount a box on either side or on both swing arms if that is desired. There is more flexibility in bumper arm storage and carrying design - Tire, boxes, bike racks. Depending on the age of your existing rear bumper, it is lpossible the new square design can be installed on the pivot post.
Let me know if you have any interest in Aluminess products, I have an account with them and I like to help out forum members. I can handle the order for you including will call or drop shipping. Just drop me a PM with your interest and phone number.
Beastie 3: 2002 7.3 EB Cargo: Agile TTB, CCV Mid Top, Custom Walk Through, Lots of stuff added. BlingMyRig.com