It may be hard to tell with the missing battery tray, but this a picture looking down into the hell hole. Battery tray or not, the rust probably made that obvious. Try not to look directly at the rust. If you do you will become lethargic and loose all motivation. That's what happens to me, anyway.

Click to view attachment

Where is the green wire (marked with red arrows) supposed to go? The PO has helpfully wrapped it with blue tape marked with a question mark. At first it looked like it was routed down between the engine tin and the HE outlet, but now I think the blade was just stuck down in there to keep it out of the way.

This is a '75 1.8 with stock FI.

Mike

The only green wire in that area should have a black stripe on it. If so, it's for the temp gauge sending unit.

Goes from there under the engine tin, along the front of the engine and to the "taco" plate with the temp sender ...

Andy

Connect it to the oil temp sensor wire from below the tin.

The rust doesn't look that bad... fix it and get on with driving!

Will the sensor be there even if I don't have a console with a temp guage?

Not originally. The Cap'n

AGREED! Mine is (I beleive) the original wire, but is run the exact same way. Should run from temp sender to guage.