My 70 Challenger also came with one..... it is absolutely terrific! I found a one that was rough & needed repairs off ebay a while back and put it in my '74 Rallye. They can get twisted a bit and don't want to slide. I spent some time on her, cleaned it up and actually had to spot weld a new bottom plate on one side (rust). It's not perfect, but you can't see it and it works! I especially like the tilt function..... really helps my back on long trips. I wouldn't go back to the straight seat unless I had to......
VT Mopar