6.2 diesel Timing chain/gear question

1983 Suburban C20 Silverado.. There are over 600,000 miles on the original motor... had the injection redone 3 times thus far, but other than that, the motor has not been into
(other than thermostat and waterpump several times). 700r4 has grenaded too many times to remember (but the lifetime warranty at SCAAMCO is still in-effect.... definitely pays to get the lifetime deal)
Okay, honestly, I haven't had to do $hit to this motor except change failed accessories, so I really have not read-up on it at all. I was, for the longest time, under the impression that the motor had timing gears connecting the crank and the camshaft. Thus, I never thought twice about the timing chain. However... a friend of mine recently said he worked on hummers in Saudi, and says "oh no, they have a chain.." He said the gears are simply to run the injection pump. Okay, well I am willing to believe that.
Here's the question ... anyone changed a 6.2 timing chain? If so, what mileage did you do so? I'm getting quite worried now... I'm sure that the chain is on borrowed time after all these years.. I'm hearing something at startup and on deceleration that "sounds" like the chain slapping the sides of the timing cover.. .it's not a horrible noise... *yet* ... But I want to know if I should stop driving this thing right now. It's slated for a rebuild ASA(financially)P... the only reason it's not in the garage sitting is because some fine fellow stole my license tags from my daily driver and I haven't had occasion to grace the DMV with my presence.
Anyone used the timing set on this page? http://www.dieselservices.com/webstore/moreinfo.cfm?Product_ID=1&CFID 767& CFTOKEN#257800
I put a straight-cut (or "noisy") gearset like that into my brother's '71 mustang with a 351c and it makes a *sweet* whine, but I'm not sure if I can deal with that noise on the diesel as it is a constant noise and changes in pitch with engine speed. You can definitely tell when an engine has straight-cut gears.. Anyone know of an angle-cut gearset? Really, why anyone would want a noisy gearset except to show-off is beyond me.. Just seems like uneccessary added vibration because of the mesh of the teeth. The angled ones seem to sort of just glide off each other while still pushing. Heck, everything on a Detriot Diesel (at least the marine, 71-series ones) is gear-driven -- by angle-cut gears.. I can't imagine how much louder those screamin' detriots would be with noisy gears!!
Ok it's late, sorry for drifting!

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