GM camshaft sprocket and timing chains

As you know the D-225 was originally equipped with an aluminum/nylon camshaft sprocket.
GM #1195077 (camshaft sprocket) was used in combination with GM #1359707 (timing chain)
These nylon sprockets were installed with an intent to quiet the noise of the original "Link Belt" brand timing chains.

Like timing chains themselves these nylon camshaft sprockets have a reputation for limited service.
My current engine rebuild is a 1966 Dauntless.
Apparently this engine had never been fully rebuilt because the bores and bearings are standard and are well worn.
Have not measured yet but I'll probably have to bore this engine .040 over.
The currently installed worn out timing sprocket is not the original nylon sprocket that GM installed.
The current sprocket is dated 8/1975.
That is the only way I can estimate the Jeeps mileage when the nylon sprocket was changed over to this cast aftermarket camshaft spocket.
The current timing chain (need to determine the manufacturer) has been in use since 1975.
It apparently was still working but it was getting rather stretched.
Also both original dampers remain intact and show signs of normal wear.
I imajine the current worn chain would have "jumped tooth" by now if the dampers were not intact.

My question is what Jeep mileage and or experience have others had concerning the original nylon camshaft sprockets ?
Furthermore what mileage and experience have others had concerning the service life of various brands of timing chains used on the odd fire V6's ?

 

The 225 in my Hurst had approximately 60,000 original miles when I pulled it, still had the original gears and was surprisingly in good condition. Pulled apart a few others that had north of 80,000 that still had the nylon. Not a 225 but the 304 in my Commando had around 90,000 when the gear finally let go, during a snow storm, mid winter in Winnipeg Manitoba.

 

67 camaro with 327 & about the same mileage as yours...started loosing pieces plugging my oil pickup every few miles during a snow storm, mid winter in the middle of Kansas...

 

My 225 tux had about 63,000 when I changed from the original gear and chain. The dampers were in very good condition.