The one thing that is rarely discussed is the active suspension/stability control. The factory cars are shockingly forgiving which makes them such a pleasure (and safe) to drive.
Local custom shop put a HC 6.2 in an old Duster, shop owner said it was pretty much impossible to drive. Local guys tell me about their modded HC going sideways, my guess is the stability control can’t keep up with the higher power.
One of the reasons with I went for the S2 kit is to stay within the veil of factory specs. I would not be surprised if the S2 software also included mods to the stability control.
Friend of mine has a C7 and a Cobra replica. He doesn’t dive the Cobra much. Besides everything else, he says it just sits and spins.
Conclusion, you can build a very high HP car, but will it give you the things that make you happy?