The conversion plate is to allow you to fit an EFI inlet manifold to an MFI head. However you don't need a conversion plate cos the FRST block and head will be EFI and not MFI like in the escort.
You would only need the coversion plate if you were fitting the FRST inlet to your Escort's MFI head to do an EFI coversion but not worth it cos you have fooked the engine anyway.
Would be easier to get the FRST loom as well but you will need the OFAB/OFAC setup from the FRST. Have a look on RS Bible which helps explain things.