325 is defiantly the car to go for its an iron block and practically indestructible
The gearbox are the same.
the lsds are next to useless by now unless they have been rebuilt but for drifting your better off sticking either a welded 325 diff or you can use a 320 diff for a higher ratio but you will need to change drive shafts and half the prop.
The biggest problem with these cars now will be rust and worn suspension/bushes. You can replace the suspension very cheaply with ebay coilovers they are very stiff buy perfectly ok for skids. The bushes are a pain in the arse but will definitely be shot by now. Replacing rear subrame and trailing arm bushes made such a difference on my e36. As for rust expect all the usual places to be bubbling by now all arches, boot lid, bonnet but again if its a drift car this really wont matter just make sure you have a good look under the car and check for excess rust where the sub frame is attached.
Other than that dont worry about it too much parts are cheap so if anything breaks it can be easily replaced. Just go out, do some skids and have some fun!!!