http://www.forabodiesonly.com/mopar/showthread.php?t=54421&highlight=go+wing it would be nice to have the under neath brackets,,,that way it will not distort the crap out of your deck lid...also do you have the 70 rear decklid with the cut outs underneath it for the brackets..it may be 71 or 72 aswell....some one on here may have the brackets for sale..
I got my measurements for my 71 Swinger from the Year One catalog. I am going to make some larger brackets for under the deck. I am using 1 1/4 fender type washers.
I took this reference pic at Big Daddys.