Need help finding Hydraulic shocks

I have chopped up the DB30 and adapted a rear swing arm with rear shocks. I need help sourcing out a proper shock. With the two shocks in place it is too rigid and the spring rate is too high. I didn't realize that the shocks are rated at 520lbs a piece, with one shock in place it is perfect. Does anybody know a shock with around 520-650lb spring rate or to shocks combined to equal around that. Thanks fellas!
There are go kart and mini bikes shocks. The set from Northern Tool is a tad stiff on a shock to seat but getting close to right if you have a swinging arm PLEASE POST SOME PHOTOS of your swinging arm conversion I'm collecting the how to's for making my own swinging arm on the DB30.
I found a shock that should be good, I just bought it for testing and will take a video of the suspension travel/articulation. I need to clean up my welds and get a the auto chain tensioner figured out, pain ad then it should be done. :scooter:
Next will be a cheap way of doing a springer front end. I am going to be using some old mustang valvesprings and weld them together!! Spring rate is about right!