[Pharo-project] How to declare Zinc/FS dependency in Metacello Configuration for 1.4

I'm updating some Metacello configurations and I'm wondering how to declare the dependencies on stuff that have been integrated into Pharo 1.4 (e.g., Zinc, FS). Should I declare those dependencies into my configuration? If yes, against with version? My gut feeling is that I should create a new baseline that does not require any Zinc of FS. That becomes a pain in the ass when developing in parallel for 1.3 and 1.4. Is the only place where I can differentiate 1.3 and 1.4 is in the stable symbolic version, right? What are people generally doing? Cheers, Francois