[tbenvie]

AMC sent the upgraded 70 kit to the SS/AMX owners purely as a marketing idea. The 70 AMX had a big facelift-nose, taillights, interior, and wanted to promote the new 70 model line. The heads were also much better, and larger head bolts as well, but this was never part of the upgrade. Didn't other manufacturers change grills/taillights as well to upgrade to a newer model year?

The improvement of the heads was not done by Kaplan, but rather in-house by the engineers that ran the flow bench and other testing equipment. They tried to sell the idea to AMC when the 390 came out-and improvement that actually cost no extra money, just a redesign casting. One of the engineers actually raced an original SS/AMX at the Nationals-the purple one shown in the staging lanes. he later helped write Performance American Style, a early "bible" for AMC enthusiasts sold at the dealers parts counters. AMC and Hurst redid the original set of heads used on the prototype Super Stock car, but did not have the time/facilities to do a run for all the cars, so sent them to Crane.

Spoke to the original owner of an SS/AMX yesterday. He also swapped the parts to an upgrade 70, but as he only raced at a local track he did not have to change them back.