K-10/K-20 Spring Pertch width

[Terraizer]

Does any body know what the front Spring pertch width is for a 1967-1972 K-10/20? This is center of the LT spring pertch to center of the Rt spring pertch or center of Lt front spring to center of the right front spring. Are better yet does anybody know if a 73+ chevy truck front axle will bolt into the front of a 67-72 K-10/20 with out messing with anything (pertchs, springs)? Thanks for any help. I'am planning on converting my 71 c20 to 4x4 and the 73+ alxes are easier to find around here.