GM was first to offer a street engine with 1 hp per cubic inch in their 283 with fuel injection.
Put a good OHC head and turbo or blower on a Burtz and I think you could produce 450+ hp. You won't get it using the stock A intake/exhaust ports. I also think you can't get enough lift out of a cam that will fit through the stock cam journal size.
Today most NA race engines are 2-2.5 hp per cuin. My 310" Cleveland is 650 hp with a single 4 bbl.
Ya gotta love a guy with a dyno in his backyard.
400 hp B engine naturally aspirated -
https://www.youtube.com/watch?v=IejbsUzmVI0
part 2 -
https://www.youtube.com/watch?v=7dswKW6g6bo