Papa,

You'll start to really enjoy your runs to the auto parts store.
Do what I explain that your car is a custom race car that will be street legal and then wait for the stupidity to begin.
When they ask you the stupid questions, answer with precise accuracy by giving them the Make, Model, Year, Engine, Transmission, Etc, Etc, Etc.
Let the tap on their keyboards and look at their screens, then tap some more until they get frustrated.
It Gets Better After 10-15 Minutes, Then They Usually Finally Understand & Really Try To Start Listening To You!

Steve