From the early 70s to the later 70s you do not need to trade out anything. It is direct replacement of the speedometer.
http://www.78ta.com/smf/index.php?topic=22157.0
I am a member on that forum. You may want to join and ask, or if not I can ask for you about the 80-81, I have a feeling it is pretty simple though
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78 Trans Am--Pontiac 400-custom headers-pypes 2.5 X system-edelbrock intake and carb, pro comp roller rockers custom brackets-head work-custom sound system - recaro interior
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