Here is the first of 2 videos showing how I put this thing together. I have a lot of the same questions and I hope to cover those questions in these videos.
Remember, this is a dangerous mower/toy and it should not be built by anyone. It's also freaking awesome!
This is the link to the motor and gear boxes I used. https://www.amazon.com/dp/B07YZGF885/ref=aod_recs_desktop_prsubs_0
Here are the hub adapters.
ride+on+car+wheel+adapter%2Caps%2C115&sr=8-2
The tire/wheels are from Harbor Freight.