21tm if you can find a cheap one. Not really worth $300 though. It does have better acceleration then the tz, but the top speed is just about dead even. A local racer is getting out of MT racing and has a 1/2 gallon used 21tm. I think he might have a 18tz with a little over a gallon on it as well, but that might be spoken for. If you are interested send me a pm.