Happened to me running nitrous. Detenation but no damage. I got lucky. Replaced it with a Lincoln Aviator pump but that was on my old Mustang. I'm running a SVT Focus pump on my current Mustang.
The most I've seen naturally aspirated from a 2 valve is 318 rear wheel horsepower. I've seen 400+ rear wheel horsepower on naturally aspirated 3 and 4 valve engines.
That's not the truth. They are CARB legal up to 2003. I have a 2004.
Proof from CARB EO# list. Look up the Supercharger systems.
http://www.arb.ca.gov/msprog/aftermkt/devices/amquery.php
Saleen had an optional Vortech supercharger for the XP8 Explorer as well.
As for the Harley Davidson F150's, Ford is offering a supercharger on those again. 450hp I believe.
I went with a Vortech Mongoose kit over a Kenne Bell 2.1L kit for 2 reasons.
1. Vortech Superchargers are CARB legal. The KB is not.
2. Vortech and Modular Power House's customer service is 1000x better than what Kenne Bell calls "customer service".