FWIW I have an '89 Peugeot Versailles which is more or less original. The seatpost is about 23.8mm. There is no sleeve in the seattube; the seat tube is necked down at the top to this diameter.

@ the OP, is there a reason you need to replace anything in the drivetrain? You should be able to maintain & use what you have, unless there is something damaged or that you're otherwise dissatisified with.