Re: Rear springs
I can't say for sure but generally the difference is either height between the spring and frame, or OEM holes drilled into the frame making it easier to install. Best to contact the manufacturer in this regard as to get an older unit to work in terms of installation would just mean you would have to drill a couple holes into the frame rail to install the air helpers.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!