The 401 under the hood of the WHATIFX has had the heads changed to the 1971 AMC ....291C heads. The engine also has cloyes roller chain, headers, mild cam, Edelbrock 800 cfm carb., Edelbrock Air Gap RPM intake, and the Mallory vintage dual point distributer. It runs GREAT and is INTENSE to drive. It has already sheared 2 axle keys on the rear axle, so it has the hp to do that. It now has moser solid axles.