The X-frame is a variation of the "backbone frame" which was used on the Dodge Viper.
Ford on the other hand, ballyhooed their "perimeter frame", with some very graphic TV ads for such, back then. In the 1958 Ford ads, selling how much safer their cars were, they had a rolling chassis with a front seat and steering wheel installed. A man was sitting behind the steering wheel, as if driving. A wrecking ball was swung at the frame (with the man sitting on the seat, seat belted in, which was another safety innovation Ford was also selling). The ball smacked the frame beside the driver. The rolling chassis was knocked sideways, but the driver was never touched. Somewhere in the mix, there probably was a picture of a GM X-frame for comparison. There are some other YouTube videos showing how much stronger the Ford frame was than a similar 1957 Chevy frame was. As in gussets at the rear of the frame on the 1957 Ford frame.
There are MANY YouTube videos comparing Chrysler and other make vehicles "On The Test Track". In one 1958 video, the New Yorker is on a rural road. A train crossing is encountered on a downhill section of the road, with a sudden drop just past the train track. The Chrysler might have bottomed out, but responded well, whereas the '58 Buick Roadmaster bounced off of the bump stops a few times, PLUS the bumpers moving a good bit to "touch" the nearby body panels.
Chrysler Products might have ridden a bit firmer than a similar GM car, plus have been a bit quieter on smooooth roads, BUT the torsion-bar/leaf spring Chryslers were the DRIVER's car and a safer freeway flyer, by comparison. ONE reason they were preferred by law enforcement departments, before 1957 and well into the 1980s.
Checi out the Ross Roy "On The Test Track with the 1957 Chryslers" YouTube videos. When you get that one watched, other similar ones should be in the list too.
Enjoy!
CBODY67