Yeah, I bet you are, too.
3 seconds sound clip from the Vacation (1983) movie soundboard.
You can hear this line at 00:57:27 in the DVD version of the movie.
Quote context
[...]
- What happened? How did you get here?
- Well, these two nice Indians and a man on a camel called a tow truck.
- Never heard of no one so shit-all stupid as you driving off that road.
- You must have got manure for your brains.
[...]