4.7l woes and rant

I have a 3.7 in 1500 truck 180,000 miles no trouble,but a 2003 durango, with a 4.7 ,at 118000 bit the dust on vacation. I went to a local junkyard to get a used head, owner said there's 16 durango's in a row ,none wrecked either transmission or engines bad,I pulled heads off 5 different ones,all were junk, had to go to local autoparts store he had rebuilt for $400 each or new ones for $450,went with the new,also the nylon guilds for timing chain were heavily worn ,so I replaced them as well.