What I would do? Check out the thread below.
http://www.turbosport.co.uk/showthread.php?t=147598
It is what I almost did 20 or so years ago. Went with doing MK2 Escort with SR20DET instead.
The CA18DET is the easiest bang for buck option and easiest fit in the MK1 Corty as the steering is at the back of the X member and the CA's sump is up front. Drop in fit that.
If you choose to go with the Escort steering rack mod, then the CA's sump will need little modification to fit. Nothing a custom sump couldn't fix.
Also, not sure if Geoff is still in the biz, but he is a good contact to have when a Mk1 Cortina needs a little 'boost'.
See below.
http://www.cortina-mk1.com/contact/