Ed,
Early ECU's had LOTS of problems with Radio Frequency Interference (RFI) which included things such as HT spark plugs leads (escpecially in early VN's with VERY high voltages present), radios in cabs, and airport control towers. I was employed as an Electronics Technician repairing Auto Diagnostic Equipment when VN's/EA's first came out and you would hear all sorts of stories. Like the calls the NRMA recieved from car owners stranded in the airport tunnel with cars that wouldn't run. They would tow them 100 metres down the road, and broom off they would go!!
The moral to the story is ground everything very well and mount the ECU as SGO says - inside the car away from all the RFI action. Don't do what they did with the Peugeot Mi16 and mount the ECU under the rear guard. Wacky french bastards or what
Other cars had it mounted under the front seat which is a good spot, easy to get to, and where most blokes mount MSD's and the like.
Cheers,
Craig.