Mostly some wiring
You need to modify the wiring as mentioned to convert from the amps to volts
And depending on which year cluster you are putting in you may need to move some of the wires around in the plug that connects to the cluster
With the exception of the amps/volts gauge , It’s all the same wires just in different locations in the plug depending on the year
Your existing oil pressure gauge should be mechanical with a tiny tube going from the engine to the gauge
Don’t lose the nut that holds this onto the back of the gauge
Far as I know , you can’t buy them anywhere , it’s a weird thread pattern
What’s the reason for wanting to swap ?
If it’s just for looks I think you can restore most gauges pretty easy with overlay stickers and painting the needles or find some comparable used gauges that just have faded needles which are easy to repaint
I swapped mine because the original 76 cluster had cooked in the Arizona desert sun for 40 years and I got a nice 82 cluster for free
But it was a lot of effort figuring out the wire swaps in the plug