Megasquirt/Computer Mounting

If you are leaving your Heater in place, you can mount it upside down hanging off dash. My heater is coming out so I am will be mounting my Relay Board and ECU in its place.
I will be running the wires out to the engine in the trans tunnel low so they are not seen.

You could mount the ECU under the passenger seat and put your fuse block and Relay board above the Passenger Kick panel leaving your Heater in place.

Also if you have a shift console mount the ECU under the stock shift console forward of the shift lever running the ECU tuning cable into the console storage, then mount your relays above the kick panel.