if i were you i would for a few weeks try and familiarise them with each others scents.
one way is to collect a favorite toy from each and introduce it to the other. and keep note of their reactions.
also try taking it in turns to place one if them in their carriers and let the other rome free able to approach the other cat if they want , this is a safe way of seeing how they react!
another way is to use cat nip spray to calm them, try spraying a little on favorite toy or blanket and then again leting them approach each other if they want! sometimes they will take no notice at all.. others will become agressive.
good luck!!