hopefully the gauges did not burn up when they pegged like that... the same thing happened on my 71 challenger and it ruined the gauges. if the dash voltage regulator fails and allows 12v to the meters they will peg, and the tiny resistance wire mechanism in them can be damaged.

i would check that the meters still work, you can do this with a small 9v battery as a test. With 9v applied the meters should move towards their maximum.

cheers