If the magazine uses Westech dynos they will always get the numbers they need... I agree 450hp with that MP .484 cam is way optimistic.
Stroker - yes, 260cfm "could" make 520hp. However, look at the parts you have. You're saying they flowed 260. At what lift? what do they flow at .200? The MAX lift on a .484 at the valve is closer to .465 and it only spends about 50° anywhere near that lift. The "bulk" of the flow area under the curve is between .150 and .300 of valve lift. Using the Edelbrock published numbers for the RPM head which peaks around 250cfm at .600 lift: if the heads flowed say, 188 @ .300 and 129 @ .200, the engine will only be able to make the power allowed by those lower flow rates, plus maybe a little for the "push" inertia and sonic ram afffects might provide above peak torque. I'd be expecting a result around 400hp for that cam and head combo, assuming a true 9.5:1 static, proper machining, balancing, and assembly. Any of which can vary drastically from engine to engine, builder to builder, etc. It's very easy to get numbers you want from a dyno or flow bench and Westech is well known for being exceedingly "happy". The proof of the pudding is when it's running down a track accelerating a given weight to a certain mile per hour over a measured distance.