I have to agree with stepside on this one. His deskdyno numbers seem about right.
As for your friend having well over 450 horses with that set-up, I find that extremely hard to believe. I'd be willing to be he has more like 370- 380 at the flywheel if he's lucky and thats pushing it. Show me some dyno sheets for your motor and your friends and then I'll believe it. Does he have actuall sheets or is that what he thinks he has
Hope you like spending big bucks for gas as with your new setup as you will have around 10.5-11 compression. If you run aluminum heads, it won't be as bad. I'd personally stay away from iron heads with 10.5 comp for the street. I guess it all depends what you use it for.