Mine had a 19' bed and with the 8" cyl it would go back far enough to lift the rear wheels off the ground. I made a drawing of the side of the truck cab and chassis out of poster board using a 1" to 1' scale, then added the bed frame with a stick pin at the hinge on the rear of the frame, then added the lift arms adjusting the length at 6" intervals until I got the bed frame angle at 18 degrees. Then cut a strip of poster board to simulate the bed floor and would slide it back and fourth to simulate the the bed movement and measured it to get the cylinder length, got lucky and found one a little longer at the auction. Good luck and if I can be of any help let me know. Wish I could remember the cab to axle length that would help setting it up.
