360 original timing chain ?

I have a 360 in a 1979 dodge van, it has 91.000 miles on it. I'm hoping some of you guys have some experience with these older engines and can advise me about the timing chain. It has the original timing chain in it. I was wondering if these chains were nylon(plastic) and are known to go out or do they last for alot more miles than 91K. Thanks!