I converted my own bike to this, it's absolutely brilliant but if you want something with a longer range (this will do about 28 miles on the highest peddle assist and about 12 miles on the lowest) also you can use a cheat code to do 20mph instead of 15mph (UK legal limit) also I use a thumb throttle (illegal in the UK) but I don't give a fuck.
https://www.swytchbike.com/
https://www.swytchbike.com/