True, the larger motor has larger airflow requirements because it's making more power, so you would need to step up to a larger turbo. I should have said "you can bolt up turbos to any size motor"
As for not seeing any big block road race cars... where have you been?
Rulemakers only limit engine size to control the speed levels. Have you ever noticed that in Pro Stock, F1, Indy, and Nascar, they
all run up against that limit? They NEVER run a smaller engine because it just makes them slower and less reliable. Small engines suck. They are only run because it controls the overall speed.
btw, Can-Am was essentially unlimited, and 540 inch engines were common. This was probably only limited by the lack of aftermarket blocks able to go bigger. The Corvettes and the Saleen S7's that run in ALMS are 427 inch, the Viper is 488...