The improved weight distribution will certainly be a great thing, an example of good attention to performance chassis basics rather than trying to bandaid a mediocre chassis with ultra wide tires and ultra stiff chassis to rack up impressive, if somewhat artificial, test track numbers.
The all AL block and locating the battery well back in the engine bay should hugely improve not only overall weight and weight distribution, but just as importantly, the chassis moment of inertia -- i.e., how far out are the masses located from the CG and thus, how much inertia must the chassis overcome to effect a change in direction.
The current Stang, with its heavy FE block and battery located way out far from the CG, coupled with its short WB which gives it scant leverage over that far flung mass, is about the opposite of how a good, responsive chassis should be designed (amongst a multitude of other dynamic shortcomings).
The Next Stang, by dint of its improved weight distribution and mass centralization alone should be much more agile and adept dynamically. The overall front chassis design also appears to be worlds better than the current car and that should realize not only improved hard numbers and raw capability, but just as importantly, vastly better feel, feedback and balance.
As for the weight distribution's impact on rear
suspension capability, especially over broken/uneven surfaces, that would be a small though welcome improvement. Basically you'll slightly improve the ratio of sprung vs unsprung mass, which is essentially a battle between the two masses as to which moves which more. However, the biggest and most significant variable in that equation still is the unsprung mass, i.e., moving
suspension components. And with all else being equal in regards to the rear
suspension design, a live axle's huge unsprung mass still puts it at a very distiinct disadvantage to an IRS and its resultant ability to react to an uneven road surface.
Again, this inherent disadvantage means little on the drag strip where the rear
suspension basically doesn't move at all anyway and thus, the overall simplicity and (presumably) resultant robustness of a live axle do come to the fore. A similar situation also exists on very smooth roads and curves of any sort where the
suspension basically is moving very little. That's why live axle cars can often do quite well on very smooth roads and road course tracks against IRS cars because neither
suspension really is being taxed to do much in the first place.
When things get bumpy and more challenging however, as they usually do on most roads, things don't look so sanguine for a live axle. You can always resort to very stiff springs, shocks and bushings in an attempt to reign in a flailing live axle, but that comes at a very high detriment to ride quality, suppleness and the ability to accurately trace the road surface contours and maintain contact, traction and adhesion. A good IRS on the other hand, with far less mass and inertia to overcome, can far better follow the road surface contours with softer, suppler, more compliant shock/spring/bushings and thus maintain a much higher level of contact, traction and adhesion at far less of a cost in terms or ride quality -- sort of having your cake and eating it too.
This does, of course come at a greater cost, both in terms of coin and complexity. Whether that cost actually represents a good value to you really depends both on the depth of your wallet and your intended use for the car. If its limited to simple drag strip use or very smooth road driving, then perhaps not. If you desire a much broader and more widely capable performance envelope over a variety of real world road surface conditions, without jarring your fillings loose, then I would suggest the IRS does represent the better value.
