NOT trying to talk you out of a lift. BUT, its NOT likely your springs are shot after 100k miles, unless the suspension was abused to the point of damaging the springs.
I've had tires near their end of their tread life, make a vehicle feel like it was floating as well.
More likely just your strut/shocks are shot and maybe your sway bar bushings are shot as well, do an inspection and see if there is anything else that looks suspect.
If you're going to do a lift anyway, then by all means do it. But if you want the OEM ride back, it might just be a set of new struts/shocks and maybe swaybar bushings.
Last edited by Mongo; 11-03-2014 at 04:39 PM.