ATK engines 408 sroker with Magnum block LA build

Is anyone using one of these ATK engines? They're using Magnum blocks with an LA front cover set up for a mechanical fuel pump.

It sounds to me like a great combination. You get the hydraulic roller cam with the better flowing Magnum Edelbrock aluminum heads. And It Bolts right in place of an LA engine.

They are rating these at 465 horse, 535 torque.

Is there a downside to this engine?