There are two water pump depths, also. Early 1969 cars used a pump with a 4" dimension from the hub face to the mounting surface. Late 1969 through 77 used a deeper pump. Make sure you get the right set of pulleys and spacers for the year/pump style you're using.
If you have A/C, the compressor bracket attachment scheme changed in 69. IIRC, 69 and newer front brackets mount to tapped holes in the heads.
1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base
Last edited by jmt455; 12-17-2012 at 06:59 PM.
Reason: added details