DZ,
70 model's did use an electric trunk opener, the solinoid/latch was mounted in the trunk lid, and used the lid for its ground. In 70, and some on 71, I'm not sure how long the same switch was used, mine came from a 71 SS454 Monte, the switch was a little black button mounted inside the glovebox, a hot wire from the fuse block feeds it, then it ran down the passenger side of the car, ( under the carpet ) and entered the trunk behind the rear seat, and was clipped to the hinge. then it ran up through the trunk lid about like the trunk lite does.
The solinoid/latch is the same one that is used in many early GM products from the early 70's, late 60's also. I've found them in Olds and Buicks. If you would like to see the setup, send me an e-mail and I'll take a digital pic of it.
One other thing, the replacement switch that is available from GM, started being used later, it works fine, but it's not the correct one.