I was at a salvage yard last weekend and almost nabbed the rear springs off a 76 K20. My truck has the HD front spring (3 leaf) option, but not the HD rear leaf option, and the front sits noticeably taller than the rear (that HD front spring also rides like garbage). My dad said he remembers the truck being nose high like that since the day it was new. I figured the 8 leaf spring on the K20 might raise the rear a little over the 6 leaf on mine, but I'm guessing that 8 leaf is 56in instead of a 52in. I've read on at least a dozen threads on this forum that K10 and K20 frames are identical, and that the frame already has holes drilled to move the rear spring mount back 4 inches for a 56in spring. My truck sure doesn't have those second set of holes in the frame. I would have to drill 8 holes in the frame if I want a 56in spring. I'm curious to hear what others' thoughts are, but it seems there's some incorrect information floating around about the frames.