150/200 is still too soft. we will have to go much more rate in the rear to get 3" more of shaft, and 2-3" preload.
with 125/200 on there now, 4" shaft showing, 3" preload, math says thats 1000lbs per back corner corner- i cant imagine that is correct. (not ignoring angles would make that number even more)
with that same 1000lbs to get 7" shaft with 2" preload, id need a rate of 110lbs/in or like 200/250 or 150/300
not sure if parts shocks will allow dual rates on back shocks