So a couple things. First, the Bilstein 5165's cannot be revalved. You'll need to replace the whole shock with something with stiffer valving. Second, 255/70 is Bilsteins standard shock valving, so a large majority of their shocks have the same valving, just different lengths according to the application.
If you want to get into revalving shocks, you'll need to spend a little extra coin to get something that can be tuned. Bilstein has the 7100 series shocks that are their entry level rebuildable shocks, but I honestly wouldn't waste your time buying Bilsteins if you are wanting to get into tuning your own shocks. The parts aren't as cheap or easy to find, and finding information on tuning their shocks is almost non-existent. It's worth spending the extra coin on any of the other top manufactures to have easier access to parts, valve stacks, and tuning information.
I have the 7100's and I can't really complain about the performance at all. I've beat the hell out of them and the shafts are still in good shape, unlike what I've seen from other manufacturers. The biggest complaint is the lack of support. I've gotten to the point that I'd rather just buy new shocks with stiffer valving than try to mess with these.