As to the C&C carnage the real blame rests with stupidity and lack of driving skill. Lethal combo. The stick axle is a convenient scape goat.If it is an HPDE toy, the Mustang is plenty capable. My car is mostly stock, but I still feel I haven't been able to utilize the car to its fullest potential yet. It's a lot of car. Stock for stock a C7 will be a better performer, but a good driver in a Boss 302 will be able to hang with an average driver in a C7.
If you like your Boss 302, I say get more seat time with it before deciding you need to upgrade. The solid rear axle really isn't a limitation on track. It is the car show and cars and coffee crowd that blames the solid rear axle for their wrecks when leaving a parking lot in front of an audience.