I revisited this thread only because I wanted to figure out why the earliest 3G trucks had rear coil-overs available where later 3Gs didn't.
The first listing is for a 2005 Ram 2500 mid-line Gabriel shock specifically listed for 4X4.
61716 ProGuard
Specifications
Product Line: ProGuard
Shock Extended Length: 26.5 in. 673.1 mm.
Shock Collapsed Length: 16.33 in. 414.78 mm.
Length of Stroke: 10.17 in. 258.32 mm.
Accessory Kits: n/a
Upper Mount Code: ES34
Lower Mount Code: ES34
Weight 5.75 lbs. 2.61 kg.
Dust Tube Material Steel
Package Contents n/a
The listing below is for a 2002 Ram 2500 coil-over. You'll note the mount codes are the same, but I bolded the essential difference-length.
43181 Rear Load Carrier
Specifications
Product Line: Rear Load Carrier
Shock Extended Length: 24.24 in. 615.7 mm.
Shock Collapsed Length: 14.88 in. 377.95 mm.
Length of Stroke: 9.36 in. 237.74 mm.
Accessory Kits: n/a
Upper Mount Code: ES34
Lower Mount Code: ES34
Weight 15.47 lbs. 7.02 kg.
Dust Tube Material N/A
Package Contents 2 Shocks
For S&Gs, here is a mid-grade Gabriel rear shock for a 2005 Ram 2500 4X2 >8800 GVWR.
61710 ProGuard
Specifications
Product Line: ProGuard
Shock Extended Length: 27.58 in. 700.53 mm.
Shock Collapsed Length: 17.14 in. 435.36 mm.
Length of Stroke: 10.44 in. 265.18 mm.
Accessory Kits: n/a
Upper Mount Code: ES34
Lower Mount Code: ES34
Weight 6.3 lbs. 2.86 kg.
Dust Tube Material Steel
Package Contents n/a
Clearly, this is a matter of ride height of base vehicle configurations. It seems that there is either a shock mount height difference or a lift block under the leaf spring packs accounting for the difference. The 2005 4X2 shock is ~1" longer than the 2005 2500 4X4. And the 2002 coil-over (non-specific application) is ~2.75" shorter than the 2005 2500 4X2 and ~1.75" shorter than the 2005 2500 4X4.