[71sierragrande]

Need a core support, grille, hood latch, and fenders to switch to 69-72 chevy.
Need a core support, grille, hood latch, and hood to switch to 67-68 chevy. Note: GMC changed the bumper in 69 with little indentions for the turn signals. It's minor, but you'll have to change it to be correct especially if going 71-72 chevy, which has the turn signal hole cutouts.

As far as the fenders are concerned, it's simple. All 67's are the same and have no marker light hole. All 68's are the same, and identical to the 67's except they have a marker light hole. All GMC 68-72's are identical to the 68 chevy with the marker light hole(in other words, GMC never changed the shape of the fender).

Here's where the change came in: In 69, chevy changed to a recessed front lip, so the 69-72 chevy's are unto themselves. And the grilles for those years will only fit those fenders.