Revealing mistake: As the truck tips to the left, the stunt driver is seen steering, and appears to be activating the ram to finish the stunt.
Revealing mistake: When the thug with the blade sticking out his back is standing still, there is some kind of squared device on his back under his clothes, presumably to retract the fake blade to end the sequence.
Answer: The scene you describe was indeed filmed. It was cut out of the US release of the film although I cannot speak for the Australian version. The scene also appears in the Marvel Comics adaptation. http://www.theraider.net/films/raiders/deleted_scenes.php has a list of this and the other deleted scenes.
Phil C.