I have done this on a 500E...If the oil changes are neglected EVER, or if the chain tensioner rattles even the slightest on start up, I'd have this done.
You will need the rails, tensioner, and a new chain. ( This is how we do it and we have had no problems)
Specail tools are required, be sure the shop has done this before.
1991 GMC Syclone
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