Are after market pedals legal in street?
There's no allowance in Street for aftermarket pedals. You could try arguing that they're a comfort and convenience item, but I'd expect you to lose that argument at a big event.
Given the concern about gearing and shifting, consider another option: an automatic transmission. Besides the increased ease of shifting, in the Camaro's case at least, the auto arguably has better great ratios. The downside is that auto cars often have softer suspensions or are otherwise compromised -- I'm pretty sure that's the case with the Mustang.
I know Ken drove a Boss 302 and didn't love it maybe I can convince him to get a 5th Gen 1LE
What didn't he like about the Boss? It's the FS car that I have the most irrational lust for.