The early Pre B's used a staked on front sight, similar to a 1911, except the tenon goes down through the barrel bushing and holds it in, too. It's hard to find front sights for those.
The later Pre B's (still no firing pin block safety in them but they have the pinned in front sight like the B models.
Some Pre B's have a rounded trigger guard and some have the squared off trigger guard of the B model.
I think there's more than one "transition" model of the Pre B guns.
The Pre B CZ 85 parts (safeties, slide releases, hammer are still available from CZ Custom). I know, I ordered those parts and installed on a modified CZ 75 Compact so that it looks/operates like a CZ 85 Compact.
The single safety for the Pre B CZ 75 are not. If you get one, be careful and don't lose any parts to the safety.
I was thinking if I ran across another CZ 85 (Pre B or B) I'd buy it just to put away since they appear to no longer be in CZ's catalog.
Good luck with your search.