I have 2 friends, each with an old el camino (one is a 71 and another is a 72). Anyways, both of their cars don't have right side mirrors, and it is legal to leave it that way... something about how if it came like that when the car was made, you don't need to have it.
I know it is random, but this reminded me of that
by the way, have you driven the car without this mirror yet? I bet you need the mirror for safety issues... the car has some pretty big blind spots.