Carb issue?

As has been mentioned by the OP, Edelbrock lists the normal operating vacuum for the 7177 cam, with its 308/318 degrees of advertised duration, as 10-12”.
So, reduce that by about 7” for the 6900’ elevation, and you’re in the 3-5” range.
This would be normal for that location and combination of parts.

So, it just makes sense that the motor needs a carb bolted onto it that can adequately supply enough fuel for a strong idle with only 5” vacuum.