I went to them back in the late 70's on a 440-6 'cuda I owned, the previous owner had the heads milled and blocked decked big time to bump up the compression. I think it was around 10.5 to 1. I guess he just didn't want to buy custom pistons even back then. He had the pushrods shortened to compensate for the metal removal from the important components, but he used cheap pushrods, I tossed them after I bent to many of them and went to ISKY adjustables. End of problems. Besides, they looked cool whenever I pulled a valve-cover when some Mopar friends came over.