The more the better, to an extent. Here is a thread on grounds even though it's the next gen it will help you:
http://67-72chevytrucks.com/vboard/s....php?p=4200642
A great one on ground straps but no locations:
http://67-72chevytrucks.com/vboard/s....php?p=7098376
If it has power going to it, it needs grounds.