I have driven a track car mk2 with sierra rs rear end conversion and a road car mk1 with an M3 rear end conversion and in my opinion it ruins the car.
Both cars just felt a bit vague on the arse and i couldn't get the power down off the line like my mk1 , suppose i could just be biased.
It just didn't feel like an escort if that makes sense , with my linked rear i know how far i can hang it and what the rears doing but maybe with more time behind the wheel of both the cars my opinion would change.
Without trying a converted car for yourself it could make for an expensive regret.
Don't get me wrong i am all for technological advances and developing your car but for me the conversion removed the escorts character.