I personally would build NA 540's out of your existing motors, turn key, and enjoy.

Next you need to figure out your hatch situation raised or scoops.

650-700HP going that route, and its gonna take some trick heads and a wild cam.

10-71's with chillers, 850-900HP. Still turn key with milder cams.

My blower motors start with a flip of the key. My buddies N/A carb'd engines do some cranking before they will start. Blower motors don't have to wait for vacuum to build to draw fuel in the cylinder. Setup properly they start and idle like a dream.

I say go blower. The 525EFI cam will work just fine with a roots.