I can take some pictures tonight I think (have to go see my son's teacher though, so maybe not)
I went to Lowes and bought a pair of the heavy springs. They come in different weights, and they had an assortment there.
I used 2" square tubing to enclose the springs, so nobodys hands etc could get in there.
At the end, I added another peice of tubing (this will take a picture to explain) but basicly the only sheaves I found were these
1.5"Dx7/16"Thk1/2"Hole 3/16"Cable 525Lb-WLLSheave w/BrnzBush | Fastenal
I made up some Aircraft cables with eyes on the end, hooked one eye over the spring, then the other (if I remember right, I C clamped to test) then bolted through the side of my tailgate frame.
I wanted my springs encased.
I wanted heavy steel for the tube so I can add tie downs on them which I have never done and my DW was uh,,, reminding me that I needed to do.
I wanted nice sheaves in place to keep the cables going in the right place and not binding.
I wanted to be able to easily disconnect from the tailgate as we take ours off fairly often.
The only other caution I have (and you can believe this or not) was that the wife, on the first day of use, reached down and grabbed the gate, forgetting about the lifts.... She jerked up on the gate like she would have the day before and hit herself in the face with the gate, darn near knocking herself out. She was PISSSED when she got home... my laughing did not help much either.
Will try and grab some pictures.