where to mount rear spoiler on 73 duster

If I am not mistaken, unless your car already had a wing installed, it will not have brackets (there would have been no reason for them). Also, you will not be able to mount the wing correctly unless you have the brackets and their cut-outs in the deck lid. It is not just a simple matter of drilling a couple of holes through it and bolting down the pedestals. Your vendor should include proper mounting instructions.

Sorry, I can't help with measurements right now. My son Aaron is at college with his Dart Sport that has the wing. If he comes in this weekend, I'll take some measurements.

Jerry