Don't the MK1 Cortinas have an engine code ?
Try
http://www.cortina-mk1.com/identify.php, and others I'm sure.
Never ever heard of a V8 Mk1 Cortina factory approved (someone can prove me wrong I'm sure).
There were some Mk2 Cortina Savage (approved?) conversions, with an Essex V6 3lt IIRC.