Depends on the market the donor car the glass came from in the first place.
260z stuff is as follows
General export = 4.0mm thick (ie NZ)
Europe export = 4.0mm thick
Australian export = 5.0mm thick
240z does not state other than
General export = 4.0mm thick
there a number of other part numbers for different markets, tint, temperd, heating but no mention of thickness so assume all 4.0mm thick.