I've been looking into those dragsters for a while, they are cool, i just dont have anywhere to drive one all that much,but i think ill still eventually get one. for a dragster i would definitely go with an 18 size engine for the torque of it., you can get an epic .18 from towerhobbies.com for 155,i belive that is about as much as any other good 12 or 15. even cheaper then most. the engine turns out about 40,000 rpm, and is designed with a turbo/knife edge style con rod and crank, so it will turn smoothe and fast as hell. then i would throw a very open pipe on it, and a big ass filter to get the most air in possible (then you can run more fuel with the proper mix and get more power)
the reason for the 18 is simply torque, with more torque you can run a higher gearing and still have the same acceleration as a car with less torque and lower gearing, and then you will have higher top speed... and i also like the epic a lot, in xrc cars it got a CEN (crap) car to go 58 mph ... stock.. right after break in, i htink youd like it.
if you go for a .12 or 15 the cvrs are all about 160 bones. they are great engines and will last you along time, but you might want to look at a mugen for that price ... and ya know what might be decent. a
TRX 2.5 ... traxxas cars are famous for being real fast in straight lines (and thats about all ...jk) ... hope i helped a little