At 55:50 they show that the dummy being chainsawed is only a torso, despite the actress having both legs in tact.
Right after the credits the date shown is October 31, 1976 and the radio is playing "That Smell" by Lynyrd Skynyrd. "That Smell" was not recorded until July-August of 1977. (Note for argument sake. There is a recording of "That Smell" that was done in 1976 but supposedly scrapped and re-recorded. However, was most likely not commercially available in October of 1976)
When announcing the casting of Lawrence Hilton-Jacobs, Rob Zombie announced him as being "the manager of a traveling roadshow known as The Venus Lux Happy Time Fun Show". Later, when announcing Jeff Daniel Phillips, Zombie called him "the ass-kicking carney mechanic of Venus Virgo's traveling show", inexplicably changing the show-within-a-film's-title. Zombie has not addressed this apparent memory slip.
In the opening credits montage, presumably set in 1976, an obviously modern (21st century) truck front fender is seen in one of the cuts.