cluster opinions/options

[xs-style]

I was able to pick up two clusters durring this week's autofair. I believe they are both from 80+ trucks. Im leaning towards using the tach cluster. My question here is about the next hurdle.. making it work in my '78. Ive done a little searching on the subject, but Im unclear as to what I have and where to go with it. 73-87's write up on the subject seems to say that any tach from a 78 and up should be plug and go. I was told the tach cluster was from an 85 model, so I should be ok there. However Ive also read some different writeups that involved repinning connectors, and changing the circuit on the back... What exactly do I need to do here to make sure I get this all wired up right? Wouldnt want to let any of the smoke out of the wires, now would we?