Fiesta 1.25 mk5 55 reg to 1.8 zetec

i have a fiesta 1.25 and a escort 1.8zetec silver top 115bhp , i want to put the 1.8 in my fiesta any info would help plz
i hope then to turbo it at a later date after i see how it runs and drives

can i use the 1.25 gear box ? Or will i have to make the zetec one fit ?