Those are not coil over shocks, they are what is called "Load Levelers" used to assist weak springs. Jack up by frame, yank them off (they can't expand but to the max shock extension) and install new ones. The spring rate is low and can usually be compressed far enough by hand to get on mount studs. If one can't compress far enough to mount then there are at least two easy options: compress and wire to hold or pop off front shackles and lower axle. Once shocks are in place cut wire or jack up axle till shackle straps fit. Either way being to raise and lower frame and also being able to raise and lower axle makes the job much easier.
