Dunno how much that the 1/43 scale trucks are, but the ZipZaps MTs provide quite a bit of "bang for yer buck" IMHO -
With the fastest gears and motor installed (16.2:1 - orange / 21,000 RPM - orange), and no mods to the truck or PC board, one could expect around 4-6 MPH (maybe 7, or a wee bit more) or so on flat smooth concrete. I clocked my nephew's Bigfoot ZipZap MT when he first got it (using the RS Lap Counter), and the results were 4.57 MPH.