Hey-
I have a '89 caprice that I mounted two riggers on, if you want a picture, private message me and I'll take a photo or two and describe what you need to know..... It was easy and fairly convenient.
****, just look in the back right corner of my
<--- avatar and you'll see the swivel mount and the rigger.

Jeff Bing.
_________________________
Yup, taught 'em myself!