The stock mounts are a pretty decent design for the street. They do a good job of isolating engine generated noise and vibration from traveling to the chassis and passenger compartment and have a safety strap to keep the engine in place in case the rubber isolation material fails. Good idea to replace with new mounts if you are uncertain about the age or condition of your existing mounts.
Even with the 427 I've never had a problem shifting using the stock mounts.
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