During the police chase, at least one officer's shoulder patch is reversed, meaning the film was flipped.
A few shots of the police cars crashing in the motorcycle chase are repeated, but with different camera angles.
The police cars in the motorcycle chase change from Ford Galaxies/LTDs to Plymouth Satellites in many shots.
Kirshner's men race from his driveway in the Dodge van to chase the escaped gorilla, but the next shot shows the same van parked across the street from where the gorilla runs along a brick wall. After this the men are shown speeding down a different street in the very same van.
During the lengthy police/dirt-bike chase where the cars roll over, if the hood is open you can see that the motor compartment is empty.
In many close-up shots of Ray Milland's head attached on Rosey Grier's body, it is very clear it's not Milland's actual head, but a prosthetic one made up to look like him.
During the big motorcycle chase, in a POV shot from the motorcycle, the stunt driver (doubling for Don Marshall) is on the right side of the screen, with the camera shooting over his left shoulder.
It appears that more than Kirschner's head was transplanted to Moss's body. If smoke is breathed in by one head and exhaled by the other, there must be some connection to the lungs. If Kirschner is talking, he must have a voice box. Could both talk at the same time? In spite of the science jargon, there is no evidence that anything but the head was transplanted.