The car has 17 inch wheels, I needed the ability to get the car low. The tube is 6 inches, 4 inches threaded. The non threaded part is a larger ID than the threaded part. The threads on the shock will fit into the nonthreaded part. The shock then bottoms out on the cut protion of the Z strut tube.
The rockers are at about 5 inches from the ground. THis is pretty close to where I want the car to sit.
I can't imagine a car with the rears done like the web site says. If I had left 5 inches of tube, the new threaded 6 inch tube would slip over 2 inches of that, that still is 3 inches taller that I have the car. I can still go another inch or so lower but it would stil be too high.
The part on the web site about assembling the suspension before welding is very good advice.