The Volkswagen Beetle the crew turns into a Swamp Buggy changes license plates and gains a sunroof between the planning session and the actual conversion. (See Trivia entry.)
Strictly, a "factoid" is a piece of believable, but untrue information, not a "small fact" (although, given that the Monster Garage Factoid above is untrue, it would seem that on this occasion, at least, it was used correctly).
In the "American Monsters" episode, the narrator introduces the suburban mechanics by saying their Deloreans were high style in the 1970s. The Delorean didn't start production until 1981.
A Monster Garage Factoid during the "Ambulance/Wheelie Car" episode refers to Hemi Under Glass as a Dodge factory reject. Hemi Under Glass was actually a Plymouth drag racer.