taking out a wiring harness

Locate the wires for ignition, starting, charging, and gage senders; modify them to fit your engine as needed. Beyond that, you won't really need anything else. I'm pretty sure we just ran new wires for the gages on a friend of mine's car several years ago. And since start/charge/ignition ought to be on the chassis harness, you really should be able to just disconnect and remove the engine harness completely from the car. Do you plan to use the in tank electric fuel pump or are you going to use a mechanical? The only reason I ask is, if you want to use a mechanical or an inline pump out of the tank, you'll need to drop the tank and remove the current pump. Furthermore, if you do elect to use the in-tank pump, I'm pretty sure you'll quickly exceed the output on it. Stock EFI pumps don't kick out much for volume even when run for low pressure and if you've modded the engine at all, you might run into fuel starvation issues.