After Merle and Jackie steal the car from the Sportsman Hotel and are on their way to see Murdoch, its clear that the driving scene is green screened and the reflection in the shop windows is a silver SUV and not the car that they stole.
When The Butcher considers selling his muscle car, he advertises it to the potential buyer that this is a 1969 Charger. This is not correct, as the body styling and interior featured on his car wasn't introduced until 1971. (It's either a 1971 or 1972 model.)
In the meeting between Murdoch and Doyle, Murdoch produces a grenade. In a flashback sequence immediately following, another character also handles a grenade. Both grenades have a blue handle, indicating there are practice grenades.
In the shootout at Doyle's strip club, Hench retrieves a M1919A6 Caliber .30 air-cooled Light Machine Gun from the wall of Doyle's office. He shoots up the club and Doyle's henchmen while holding the barrel. Machine guns get very hot when fired, especially the barrel and chamber. Hench wouldn't be able to hold the gun by the barrel without burning his hand.
Not only did he get the year of the car wrong, he says it has a 4spd when it's clearly an automatic. It has both an aftermarket floor shifter and the original column shifter.