HELP! I need pictures of a 77 factory tach circuit board or info!

[1774btcrew]

I am in the process of getting all of my gauges working correctly. I had pulled out my factory 77 tach when I did my custom Speedometer and Tach. The problem is I cut up the wrong year housing and circuit board so none of my gauges work correctly. That isn't the biggest problem. I have checked and it shows a 77 circuit board as one year only. I have several tach clusters and I am not sure which cluster is the one that came out of my truck since it has been so long.
What I am looking for is pictures of a 77 circuit board with tach or information on how to tell the clusters apart. I know the early ones had amp gauges instead of volts and I know the later had electric oil pressure gauges. I am just lost on what makes a 77 unique. Any help would be much appreciated. It is finally down to 100 degrees here and I am motivated to work on my truck after a long hot summer!