I do not know about the Ford motor setup with the ZF & Centerforce, but I have a 1971 Hemi Cuda convertible with a 426 Hemi that had a McCleod clutch setup. Might as well stand on the clutch it was so tough to push in. The Centerforce is a LOT easier to push in -- I would say it is not as easy as pushing in the clutch on a Ford Escort, but it is not too much harder than that.
I cannot say anything bad about the Centerforce setup -- it is definitely the best option out there for ease of engaging the clutch and hold power. Hope this helps.