I voted for the OS .18 tz b/c i've seen with my own eyes how much faster it makes a jato 3.3 go vs the stock 3.3 engine. If i were you i would go with maybe a losi .28 the mach 427 model it has was more hp which with the right gearing will make it crazy fast. You will be able to get another 15-20 mph out of the losi vs the tz or the brushless motors.