There are many options for the 8.8 beyond the 31-spline axle swap. Moser offers some ultimate combos if you are going to do some serious racing. The 33- and 35-spline axles can be used with a Wavetrac that significantly improves the bias ratio and comes with case-hardened billet-steel bodies and ARP fasteners. Combined with 9-inch Ford housing ends and bearings, you get the durability of the 9-inch with the efficiency and reduced rotating mass of the 8.8. Not cheap, but you will be able to launch the car as hard as you want.