Welcome Chris,
In addition to the info
FirstOwner69 posted from GMCPauls site, you'll also need some tubing and fittings to connect the oil pressure gauge. This thread shows the fittings that work with the factory gauge -->
http://67-72chevytrucks.com/vboard/s...d.php?t=613238
Also, most alternators need an "exciter" wire to initially provide power to the field windings. With the warning light clusters, that circuit was provided through the "GEN" light bulb. While trucks with the factory gauge clusters originally had a special resistance wire incorporated into the harness. More info on that can be found here -->
http://67-72chevytrucks.com/vboard/s....php?p=6334490