This question has many answers.
My opinion is that on the V-8 engines, you have to do the timing chain, sprockets and rails to do the job properly. The reason is the long chain in the V-8's. When the chain starts to stretch, it eats at the sprockets.
On the 6's and twin cam 4's, the chains don't stretch that much, the rails will do fine if the stretch is OK.
1992 500E (very soon I hope
1981 280GE SWB
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