Yes, they have to run 23 degree heads.

I'm not sure about most guys, but here's an example of what's out there: 620HP/590TQ 415 Chevy Hard to beat for $10K.

No CI limit, but like I said, the tires are not the best to work with. That's why the car above has such an agressive attitude. You really need to manipulate the suspension geometry to plant the car to the track. If you want to see what I mean, watch this video. Can you say pinion angle?