[Captainfab]

Lift kits for the '68 and earlier K series trucks basically do not exist other than being custom made. If you need more lift that what was stock, I would suggest changing your spring mounts to accept the '73-'87 style springs. You can then either use an off the shelf lift for the '73-'87 or use the 56" springs with a shackle flip in the rear and the 52" springs up front with the parts from diy4x.com.