Nice looking kart and great job on the resto! I've had plenty of Lil Indian and Ruttman mini bikes throughout my life and could find these on garbage day by the curb if I was lucky as a kid. They were made not far from me. Never a go kart from them though and always wanted one.
Just read through your entire build thread. Such a cool project and amazing craftsmanship! I have a 1/10 scale RC rock crawler Scout II. You need to get one and replicate it to match the other 2!!!!! It's made by RedCat. It's called the Gen 8 V2.
He's 15 and here looking for some advice. Sounds like he is having fun tinkering and learning about these fun hobbies. Trial and error in my opinion is one of the best ways to learn. Jump right into it and learn from your mistakes.