a big motor will only get you so far ... set up , set up ,setup ... and practice. tou are lookin at alky carbs,overide tranny , lockup, pingel,fuel pump,billett bowls for carbs,oof drag pipes.
cub motors are cheaper... super cubs ,dm's,dmx's all need major case work . 7 mil cubs and higher need the cases trenched for the crank. i have 7 k in my suspended drag chassis F.A.S.T. 4 mil cub -- 39pwk alky carbs, wcr 1-5 n-down overide, slingshot lockup ,cyln head dragported and cases ported by jeff at fast racing. lonestar dragaxle, dd spindle mount wheels. also have a whelie bar. whole bike wieghs around #240 lbs.
a dm or dmx motor is goin to be $$$$$$$ , custom head and pipes with alot of case work.
swingover to atvdragracers.com .. alot of good info on that site.
pm KOOLGUYSON... sonny has some sick drag bikes .