No need to pull the engine to do head gaskets.

Definitely the rails are a maintenance item, and you were real lucky. I advise atleast every 75k or 5 years, but I also advise looking at them at intervals and replacing them as soon as they start to change color. If they are amber they should be replaced. How the car is driven, heat, and oil changes are factors.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician