Any of the 2-stroke machines are fast. If i was going to build up a drag machine and retain the stock engine I would get an 85-86 250R Honda. Reason is there are ALOT more parts out there readily avalible Vs. the other two. The TRX parts are the same engine wise. If you are going to build something using who knows what engine then it really doesnt make any difference what you start with. Just dont cut up a mint or really nice overall condition machine to do it with, try to find something that already junked out somewhat.
1985 Honda ATC 350X
2003 Yamaha Banshee
2003 Polaris Sportsman 500
There are 3 kinds of people in this world, Those who make things happen, those who watch things happen and those who wonder what the hell happend.