Actually there is no need to remove the ecu or wiring harness, Woody left all this intact while running the sock m112 engine off a custom ecu, I believe he did the megasquirt system while having disconnected the Bosch motronic computer all together.

there are more than just one computer, there is the Engine, Body, Transmission for Automatics and ABS/TC. each controls it's own system. I'm just talking about making a fast semi gutted street racer, none of which will be usuable as a grocery getter, that's what the Inspection Crossfire is for.