I can honestly say I've never put my car sideways (deliberately or accidently) so I can't tell you what they are like as a drift car. Personally I don't get drifting as a dedicated sport
but to each his own.
I do know a couple of guys who use their spiders as autocross/autoslalom cars. They aren't as quick and nimble as the newer stuff, but they are competitive in their own, antiquated, foreign class.
I don't know too much about the set up they use, but I think it includes lowered springs, ill-fitting rollbars and a few other goodies. There are a few guys on alfabb.com that participate in slaloms and have discussed their modifications.
Unlike Hans I don't find that my car slips into oversteer very easily. I have to push it pretty hard if I want that to happen. It certainly doesn't do it when I'm not expecting it.
If you're going to buy an older spider, get one as new as possible. I don't think you want to drift with manual steering.