Answer to question #1. Yes I have in my 86 C10. Just check out my build thread and it has what I did. And it is not overkill by any means. It really made the truck much quieter. Post #20:
http://67-72chevytrucks.com/vboard/s...d.php?t=654972
Another member used a product that looks and sounds like it is easy to work with. It starts on post #483:
http://67-72chevytrucks.com/vboard/s...705824&page=20