You'll need to get a loom from an ERST and chop out everything except the engine loom then modify it to fit to your current loom. A haynes manual for the mk3/4 escort will have all the diagrams for the RST and you'll need a haynes manual for the mk5/6 escort for the diagrams for your current car.
I wouldn't recommend trying this conversion unless you are really confident.

MazakMan