They can, you need to drill through the door handle mecanisum so the later barrel can go through the pannel and the cam then jam the handle down on the inside. Some of the more modern handles have the barrel already in place and you could change the hole lot if you with (you'll still need to drill the door frame though)
Proper series 1 locks (also early series 2?) are actully on the outside of the door. The barrel is held by the outside leaver (most handles dont have the holder) and the barrel grabs a peg to lock the door. Got to be less secure than the later system but I bet not by much.
Drivers and rear door (stationwagon) are both the same lock wise. The passengers door is locked from the inside only by a cam or later 1/4 turn twist peg simular to window locks.
As for the windows you could fit series 2 1/4 turn things on the top or proper series 1 types on the bottem. The proper ones are more annoying and I'd only fit them if you wanted the original look (like I did on my stationwagon as it had them from new, but someone took them off) The series one type require teadiusly unscrewing all the way before opening the window. Impachent passengers don't undo them all the way and then scratch the plastic windows with them!
