Court recently posted a review on a Dillenger front drive wheel kit. The video includes all the details. It's fairly simple to install. Lots of questions to ask like price range. Do you love the bike or just want something at a low price.
High performance kits show up on EM3ev's website. He's in Hong Kong. Many kits are not low priced. Leed is pretty low power and uses an on-off throttle, I think. That's not ideal. The tech zips along pretty fast.
Sometimes a kit is just the perfect way to go electric when you already have a nice bike that fits just right! Share a few more details on where you plan to ride @Ray Mickshaw , roughly how far, how much weight do you think you'll need to carry or haul (say a trailer, kids, dog, etc.) and some info on your bike. This will help us be able to better guide you. There are a lot of decent choices from front hub to rear hub to mid drive with various set ups for the battery- each of these combos have a wide range of pricing, so its better to buy exactly what you need rather than too much or too little based just on $$. Court has several reviews on kits which is a good place to start. First question I always ask customers is about the bike they want to convert--the dropouts, where the axle drops in either front or rear need to be good, solid metal, not stamped to handle the motor torque (unless you go with a mid drive). Also, older bikes with less than 135+mm between the drop outs probably won't be able to accommodate a motor, which rules out many single speed bikes or at least makes for more challenges.