Don't forget the fact that alot of people on here don't modify thier cars the right way. I see several threads about running cams like the CC306 with stock tune, exhaust manifolds, converters, gears etc. So you'll look at it as a cammed LT1 but it won't run as fast as you'd expect. The guys running 11s and low 12s on stock heads have spent lots of time getting the right converter, gears, exhaust, suspension and tuning.

 

I would think that most of the difference is in suspension and tires. In my oppinion dynos are only good for tuning.
I ran high twelves with an untouched long block at 3400 lbs. It just depends on how willing you are to work on the whole package. Unported LT1 heads are good way into the tens.

Daren