Consider the following.
The Ka (upto VERY recently) uses the delightful (ly shite) 'endurance' engine.
This wonder of (ancient) technology is a close derivative to the unit used in the Ford anglia of 40 years ago with the addition of (a rather poor) sequential fuel injection setup.
Yes, it has a 1.3, push rod, cross flow head engine which rattles like Jimmy Savile, are impossible to adjust the tappets well on (yes tappets!) and are generaly worn to buggery (bore wear is VERY bad) by 60K miles resulting in an oil filler that looks like a second exhaust!
If you lifted the bonnet on a Mk1 escort, fiesta or anglia.....and compared the contents to teh lump of pig iron used in the Ka......would would be hard pushed to tell the difference!

IIRC it was Ford's intention to put a lean burn super duper economical engine in the Ka that would have produced very low emmisions. But the government of the day decreed that all cars from K reg/Aug 92 would have to have cat(s) fitted, regardless of what was under the bonnet.
All of Ford's R & D went down the pan, so they stuck the first engine that they could phyically fit under the bonnet ..... a Kent, overhead valve engine.
Apparently you can't swap engines between escorts & Kas though cos where the engine mounts are bolted to the blocks is different.