I'm probably off a little somewhere, but in general:
2 or 4wd doesn't matter
All pickups thru the late 70's had 52" springs. Somewhere they went to 56" on 3/4 & 1 tons.
I think Blazers always had 52" springs.
Suburbans usually have 56" springs.
I'm sure someone on the board will have it all down more accurate than I do.
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'68 GMC shortbox 4x4 350/SM465/T221- bought it in '83
SOLD
'72 K20 500 Cad/TH400/NP205
SOLD
'92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver
'72 Monte Carlo... sweet low mile toy
'11 Dodge Challenger IE 392 6spd... midlife car