Does any one know of a good earthing point in the boot area of an ef/el fairmont?

You'll be making it, so pick a spot with some solid steel.
pref chassis rail.

think mines just underneath the parcel tray on the chassis, do it wherever it doesnt matter just make it close to the amp or watever it is, and get a good connection

Mine is under the parcel shelf. I used the factory sub mounting holes as my earth...after I sanded the paint off. Used a nut and bolt to hold the earth lugs into place.

phong =P~

Technically there is no such thing as an earth in a dc system it is a ground. To acheive a good solid ground find some metal work where you can get to both sides of and clean all the paint and undercoat off till it is shiny metal, bolt your terminal on and then coat the whole area with a good sealant to prevent rust and moisture ingress.
Don't bother with the old wives tail of making it as close as possible make sure it is a solid ground and use appropriate size cable and you will be fine....