340 6 pack cam???

Just read a Mopar Muscle article where they took a stock 340 (281 HP), added an air gap intake, an 800 cfm Edelbrock, a set of 1 5/8 Hooker headers, and a Comp 268H Extreme Energy cam and got 392 HP out of it. Does that sound right?? Seems like a lot of HP gain for stock X heads with only those basic upgrades. 111 HP gain with only 4 bolt ons ????? Can that be?? All numbers verified on a dyno.

I think the 340's were more in the 330HP range. They underrated them for insurance purposes.