You have two choices. First is to purchase an adapter harness from a company like Rywire. The second is to get the schematics for both, figure out what wiring needs to be adapted or changed and then make the changes to your's.
I have heard of people doing this both ways, the first is more expensive, in terms of cash, the second is more expensive in terms of time and aggravation. I have also heard Rywire is pretty supportive of trying to help you, if you encounter a problem where something isn't like you thought, for example if someone already rewired something, or their is a extra dohinkiy thingamajig.
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