afaik you could get away with using the 1.9 sohc escort head it would be a little higher compession. another option that would be a bit of work but i know for sure would work because its been done and documented is a zetec head swap onto a spi bottom end. neither of which will be easy i think. even with the 1.9 head you may have issues with diffrent accesory mounting plus it would be higher compression and theirs a chance it would turn it into an intereference engine. try and pm jeffescortlx he would be able to tell you if it would work and what would need done because he swapped a spi head onto the 1.9 in his turbo escort