I'm installing the exact same RetroSound radio as what you've got -
Questions: Is there a washer and nut on the front side of your dash, just behind the larger metal ring? I'm trying to get mine flush, and seems like I can't get the knobs to sit flush with the dash because of the washer/nut on the front side of the dash. Also, did you use a support strap on it, or just rely on the posts where it goes through the dash to hold it all up? Any problems running into the defrost duct at the rear end of the radio?
Thanks for any insight!