Drifting a supra isn't as bad as a lot of people think. You do have to deal with the steering angle problem, which is probably a big contributing factor to you spinning. The steering runs out on these cars quick when you enter a drift. The s13/s14 spacers will work, but they're big. S-chassis use a 16mm thread inner tie rod. Supras use a 14mm diameter inner. So if you can find spacers for something like a corolla or FC or something like that, they both use 14mm inners. But that will get you a little better angle and the car gets a lot more fun. I'm going to start working on the steering stuff once I get some other things settled and should be coming out with a tie rod setup in the next couple months. I had prototypes made for my s-chassis setup and I actually ended up with too much angle and if you didn't transition right, the wheel would get stuck.
As for the diff, the stock diffs are junk. I took one apart, checked all the tolerances and conditions of the clutch plates and thrust washers and even shimmed it tighter so it would lock and it lasted about one and a half events and then it totally stopped working. So I welded an open diff and the car was awesome. At the last event I was at with the welded diff, my e-brake was broken and the way the course was setup, it was a long straight into a big sweeper. So I was clutch kicking 3rd with the open diff and the car was killing it.
Suspension is another thing you're going to want. You can do it on a stock suspension, but it's boring and not that much fun. Coilovers are the way to go. Check the group buy section for the ones that I designed and am selling. There's a video in there of my driving the car with the same setup on there and it works awesome for drifting. But even if you don't go with my setup, you need some stiffer springs. The stock springs are soft and lowering springs aren't that much stiffer. I'm running 1000lb/in fronts and 600lb/in rears and I think in some situations a little stiffer might even be better. But I'm happy with the all around performance of the setup, so I'm not going to change it just yet.
Now wheels and tires, drifting on sawblades is like drifting on stock suspension, boring and totally not fun. Those big ass sidewalls on there, just make everything feel like crap. Get some bigger, wider wheels. 17x9 and up at least. If you want to run a little bit of a stretched tire, you can run some pretty low offsets and the car will look awesome as well. I've been running 18x9.5+12 with a 235/40 and I love it and how it looks. And picking tires is also important. Federals are decent and cheap. There are also some other cheaper brands out there that will cut it for a little while. But use stickier tires, all-seasons and normal car tires suck. Get at least something high performance, the grip will actually help out a lot once you get going.
Oh and here's that video I was talking about,
http://www.youtube.com/watch?v=zeByCoXpB3A
That was right before the rebuilt OE diff gave up. But I think I was running 225/40 or 235/40 rear tires on 18x10's and my TIP suspension and a pretty much stock engine.
Oh yeah, make sure your engine is good and you have oil in there, because 7m's like to blow more than 5cent whores.
But most important, don't be stupid and do this on the street where there are other people around. Find a way to get into events and if that doesn't happen, I guess try and be as safe as possible, just don't bitch if you get arrested or your cars get messed up.
Tim