Actually Warren converted the whole car to 1970-here is the #6 car from my website dedicated to the cars. You can see the 1970 taillights still on the car years later-the whole rear panel had to be changed for this. Though there is no stampings on the engine to verify if it came with a specific AMX or not, I have to wonder just how many of these factory race cars would still have an original engine.
http://superstockamx.com/page16.php