Other mistake: The chunk of hair that Ted has in the car is in a ponytail, and much longer than the hair cut off in the door.
Other mistake: Even though the door was locked on the half-built car, there was nothing to stop it from opening because the pillar (and mating piece for the latch) was missing.
Other mistake: When Long Duk Dong pulls up in front of Samantha's house to drop her off before going to Jake's party, there is a drive-in restaurant tray attached to the passenger-side door of the car. On top of the tray are paper Coke cups and burger wrappers. These had supposedly remained on a tray outside of the car even though Dong was careening around at high speeds. When Samantha gets out of the car and slams the door shut, the wrappers and cups still do not move.
Other mistake: When Ted and Sam are in the half built car on the night of the dance she remarks that she felt how much he liked her on her leg, but his crotch didn't go anywhere near her leg.