I don't have a '70 to measure so I can't help you. However, if the emblem is off of the other side I just use a piece of masking paper and make a template. I use the side with tape and follow a line I can duplicate on the other side (reversed, of course), then push through the holes where the emblem goes. You can line your paper up with the door opening and the top of the quarter, or the bodyline, whichever is easiest. Then just mark through your holes and drill.
However, if the same emblem is used for both sides, flipping your pattern won't work as the holes don't mirror each other. You can still make your template as above but you will have to use it to make a second one that positions the holes in the right place.
Easy, huh?
Dallas