the iso clamp assmebly provides a shorter axle pedestals, so if you want to keep rear ride height, change the pedestals or use spacer blocks ( maybe 1" spacer blocks )

beside that, the iso clamps pedestals does have bigged center hole, so if you decide to keep the pedestals and use spacer blocks, will need to fill the center hole guide.

beside that the spring stud carries a bushing to rise up the stud getting all the isolation. will need to be removed and replaced for a shorter one if using spacer block. If replacing higher axle pedestals and not using blocks, you won't have to worry because they have room to fit the higher spring guide stud.

Dunno about lower clamp, because on 73/74 B bodies we can change the lower plate for a 71/72 plate. I have no idea if M bodies have an option like that