Mine started life as 365hp 454s. Now they make 540hp with a little help from B&M (6psi). I like the blower route although it is going to create more stress on the valvetrain than naturally aspirated. With the blowers you also get little challenges like oil blowing out of your breathers under boost that wouldn't be an issue on a n/a motor. But, those blowers sure look and sound cool.

I originally built that 454 with a Dart intake. It was a little sluggish on the low end. I switched to the Air Gap and gained a lot of low end and better idle. It did not lose any RPM on the top end(5500 RPM). The air gap is much better than the stock GM high rise intake and much more drivable than a single plane.

Just more geewiz information. Before I rebuilt that 454 Magnum. I changed to an Ultradyne hydraulic flat tappet cam, stainless marine header and a Holley carb. Net gain was about 100 RPM and 1, maybe 2 MPH. The key is the whole package working together.