After owning a few CTS-V's, I certainly would have preferred a roots style blower for my Impala build.
When I started the Impala rebuild in 2020, I would have happily paid 15K for such a creation. (I believe) that beyond 15K, and the LS swap is the smarter move for big power. I had investigated the eccentrics who "thought they could" do a roots on an LT1, but there was no working prototype that was available or could be recreated. I even searched out Keith Meese before I decided that wasn't the best option. I would NOT have given 15K to stranger who simply says he can do it because he has the cad file to machine an adapter plate, and I wouldn't give a penny to someone who feels the reverse cooling flow on the LT1 can eliminate the need for an intercooler on a roots blower. No one is using a Whipple to get anywhere near 25 lbs of boost (or 1000 hp) without a great intercooler.
Right now, I am 9 months pregnant with my RMCR Impala, but I would still gladly consider a Whipple (or similar) if there was an adapter AND and intercooler that worked without super-heating the boost charge. (Yes, I would be happy to bump out my hood to make room).
With all blowers people tend to underestimate the heat caused by compressing air. Even with an OEM designed intercooled system, just bumping the pulley size down to make more boost can create enough heat to bring down the horsepower overall.
Back to Impalas, in 1995 I had to spray a 75 hp shot of nitrous into my Vortech/Impala SS throttle body, not for any power boost, but just to cool down the compressed air from the centrifugal blower. Heat kills power, and superchargers make heat. Meth injection, gaseous intercooling, and even nitrous can combat the heat, but I would certainly want to see an intercooler on my Whipple set up.