choosing the right engine is crucial, thanks to my bed experience with lite powerful outrunner motor, may I suggest to evaluate something with a good copper mass, able to keep a lot of amp without overheat.
Check this out http://kellycontroller.com/mars-0907ete ... -p-29.html
(not the direct reference because at this moment the Motenergy site is down).
Also Golden motor are good but, for sure, not the 3kw version. You need at least an engine able to keep 10-15kw as peak power (30-60 seconds of boost). https://www.goldenmotor.com/eCar/HPM72-5000.pdf
Trial ride is, for the most of time, low speed run but its requires a lot of torque, it means that the motor must be able to keep a lot of amp @ low rpm without wasting too much power and overheat.
Higher is the voltage lower is the amp to provides the same amount of watt, if you can choose go to 72v or higher.
Last suggestion: when you choice the motor be careful to the values declared by the seller, for examples Cyclone and Revolt lie about the max power able to keep the engine (verified personally).
Here my personal experience, the frame is for testing purpose, if I will able to find the correct engine-battery-controller setup, I will swap with a trial frame.
https://endless-sphere.com/forums/viewt ... 28&t=86532