I see no reason why they wouldn't be streetable, but that probably depends on your definition of streetable. Flow numbers are a small part of the equation.
Here is my opinion on stage 2 heads vs. production: Lets compare two motors everything is identical except for the heads and intake. Both with the same bore size, piston speed (same rpm) and boost. Those three factors define how much force is available to get that charge moving from the runner to the combustion chamber.
The runners on the stage 2 heads are massive. Even the unported versions have at least 50% more volume than a ported Champion or TA head. That volume of air and fuel has mass. When the intake valve is closed, that mass of air and fuel isn't moving. Each time the intake valve opens you have to accelerate that mass to get it into the chamber. The quicker you accelerate it, the more you get into the cylinder.
force= mass * acceleration.
The force for the two motors is the same (same piston speed, bore and boost). So, if the masses of the two are different, the acceleration must also be different. In the stage head, the mass is higher, so the acceleration is lower. In the production head, the mass is lower, thus acceleration is higher. So the production head can get that charge accelerated and up to speed quicker than the stage head. In the limited amount of time the valve is open, that makes the difference.
At some point, no matter how much force (rpm, boost) you put to the heads, the production head is going to run out of steam and stall out. The stage head has the potential to go much further before stalling out.
A street car operates in the low rpm, low boost range most of the time. So there is little available force to move that charge in the runner. The production head is better in this situation. The real difference between the two is debatable. That difference may be acceptable depending on your definition of streetable.