Why are there so few blown small blocks?

I wanted a blower bad and finally put enough parts together to install a Procharger on my 413ci smallblock. Before I started building I found a 6-71 complete kit and decided to buy that. It's a competition 6-71 on an Offenhauser manifold and a Hilborn bugcatcher hat injection. I'm using Lentz 6.2 rods, Large Port Commando heads and Racetec custom pistons. I'm running it on E85 with a compression ratio of 11.5. The engine is complete and I have started it several times. Still working with the injection to my satisfaction. Will have it on the track this year. I can hardly wait to see what it will do. It was a 6.32 car with 413 N/A configuration hoping for more than that..