3 speed helps a little, i dont know about eng choices. i have a sav 25 with a hotbodies 26 in it with a 3 speed and its pretty fast. id say about 40-45 mph and thats running alittle rich about 210-215 with the body on it , i was thinking of getting a sts28 eng for it as i hear its a sick eng but i havent seen one run yet