I've seen some people with very custom cars and I was just wondering what the heck goes into making a car from scratch?

 

a lot of metal and a lot of welding

 

lol, and even more time

 

And even more $$$$$$$$$$$$$$

 

What kind of thought goes into the electronics for something like this? (I don't want to do this but I'm just curious )

 

you have no idea. I went to a place where they were doing that, and it blew me away. Even with the advanced machinery they had, it took them close to a year. The electronics are wayyyyyy complex. Especially if you want like a chip or monitors.