Seat belts began coming into common use in 1956 and this episode includes an exchange in which Dan Mathews advocates their use. When he and Sergeant Johnson arrive at the scene of the fatal wreck, he surveys the carnage and notes that Lloyd and Strayson might have survived the wreck "... if they'd been wearing safety belts."
After the owner of the impound lot awakens after being knocked unconscious, it's clear that his forehead is free of any wounds. But in the next scene, he has a large bandage on his forehead.
The suspects were driving a green and white 1956 Dodge Custom Royal Convertible. When the 2nd set of suspects retrieved the "wrecked" Dodge at the gas station, a blanket was placed on the left front fender of the Dodge to cover the apparent damage. It's also apparent that a different hood was placed on the convertible so it would appear wrecked. This was probably due to the distinctive and expensive style of the 1956 Dodge convertible's hood, which would be a terrible thing to waste.