There are a few differences between the bulkheads at the rear. The bulkheads are wider apart and run parallel to each other due to the carbon plates. The chassis is slightly wider at the rear too to allow for this.
From what I can see the front is the same but you need to buy all the main parts to fit together (bulkheads, top braces for shocks, wishbones and accessories and the front bumper set).
There will be a complete MTX3 conversion set appearing later in the year from what I hear. Not sure what the price will be. Most of the alloy parts will be made from carbon based plastic for strength and lightness.