According to post #11 on the following thread from Raycow, the wheels to use are 71-87 (4x4). The 88 and up wheels have the smaller center hole:
http://67-72chevytrucks.com/vboard/s...d.php?t=430426
Personally I would be reluctant to use spacers as they may put more strain on the studs, and may also provide insufficient engagement unless the studs are replaced with longer units.