Cheryl Ladd and Patrick Duffy (Bill) are drenched inside their convertible when rain pours over them. When they first get out, it is obvious that a trickle of rain is simply pouring in front of the camera lens and the actors are dry. (Their hair, in particular.) When the camera cuts back to Kris & Bill trying to get out of the rain, they are now both drenched and their hair is too.
When Kelly has lost control of her car she first passes a light blue Pontiac GTO with a white top heading in the opposite direction, then crashes into the same car (now parked), and finally passes the same car in the same direction and forces it off the road. As she forces it off the road, the dented fender from the crash is visible.
The black car Kelly is driving has a dark red or maroon interior but in the closeup when she's trying to turn off the ignition, the interior is tan.
The infant/toddler Kelly was found in an abandoned car during a snowstorm between Dallas and Ft Worth and the identity of her parents was unknown. Even in 1955, cars had license plates, registration, and VIN's (serial numbers) that could be traced to the owner of the vehicle. If the car had been stolen, it would be a kidnapping and certainly a manhunt for the perpetrators. If the old man was her real father, he should know more of the details.