I believe so, unless they've changed the design again and tinkered with the reel dimensions which seems unlikely to me.
I was in fact just trying to find my eight-reeler which is the newer design; my old two-reeler is the earlier System 4 and I had no trouble interchanging reels between them.
I'm sure others who actually have their developing equipment at hand can chime in with more info. If I find my eight-reeler tonight I'll swap the reels around and update my post.
I've just begun to get back into analog photography, hence my unusual response...