whats the difference between those two models, and then I will go out and check mine out to see which one it is?

Also i was looking for the hydra-lectric harness, they are expensive, but theres 4 options....i am assuming since i have two hyd levers i have dual hyds but would mine be series 1 or serier 2 and how do i tell?  and will i be ok without the harness, how does it work without the harness for plowing?