Go check out the build section, SR20's have been dropped in to S13's a million times and reading through builds is a great way to see how everything goes together and see issues others have had while doing this swap.
Basically though, the swap just drops in. All of the mounting points are identical to get the motor/transmission in the car. You'll need to modify/replace the wiring harness, modify the chassis to accept intercooler piping and if you want to be pro-active replace gaskets/hoses to ensure you aren't hunting oil/coolant leaks once the motor is in the car.
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