The link to this article can explain it much better than me. The article is using air bags, however you can use springs and the procedures will be basicaly be the same.
Also I have include a link to their "stance photos" which tells what they used to accomplish each particular look.
CLICK HERE HOW TO LOWER THE REAR OF THE 67-72s
Check out the stance photos below:
CLICK HERE TO CHECK OUT THE DIFFERENT STANCE PHOTOS


Joe - (Buckeye Bowtie)
"Remember it takes about 2850 bolts to built a Chevy Truck and only 1 NUT to scatter them all over the highway"

1950 3100
1971 C-10
1939 Buick Century