How common are timing tensioner failures? Does the current 5.7 use the metal and plastic tensioners or do they use a all plastic version? I am aware that the 6.4 uses the metal and plastic version, but is this needed upgrade for a driver 5.7 or a nice to have upgrade?

I hope this helps

https://www.motortrend.com/news/chrysler-hemi-timing-chain-defect/

50,000 cars out of millions built and it is covered under a recall? I wouldn't lose any sleep over it. If you buy a car covered by the recall find out if it was performed, if not get it done before it breaks. Out of the hundreds of these engines I have worked on I have never seen one with a broken or jumped timing chain, defiantly seen wear on the plaz tech but never a broken one.