Cross-Country Road Trip in a '68 Barracuda

fishmens67 said
As you go up in elevation the engine will be running leaner, thus run hotter.

It'll run richer, less air, same amount of fuel.
A buddy ruined a Jeep 401 years ago because it was jetted for mile high (Denver, his home) and he drove it to the east coast, pinging (lean) away.