Currently stripping an old Phaeton down to just the chassis for a ground up rebuild including new drivetrain. It currently has an english axle and diff out of a 1.3 mk2 Cortina, from spinning the rear wheel and counting turns of the prop I think its a 3.777 ratio. Question is if I fit a standard 1.8 zetec with type 9 will it munch this diff?

Will you be fitting sticky tyres or road tyres ?

The ultimate levels of traction will decided what happens.

My last first Sylva ended up as a racing car with a 2.0 zetec and the tyres were ACB10s.
The axle in this was stock Vauxhall Viva.

The diff didn't blow, but too many racing starts on sticky tyres meant that the input shaft to the pinion was sheared.
The diff itself was fine.

Sticky tyres and standing starts along with suspension set up to maximise traction will kill the axle.

Normal road tyres and wheelspin, will give it an easier life.

i used to run 2.0 zetec type 9 and 3.77 english diff lsd it was ok

I have had the same in my race car and sprinted with it for a number of years

HTH

Thanks, its going to do the odd track day but mainly a road car. Something less to worry about!