When stealing Tiffany's SUV, Gio backed out of her driveway, allowing the license plate to be seen. The annual renewal yellow sticker would be accurate, however, the county name "Broward" (or any other county name) was not added to license plates until 2008.
When disposing of Reed's body, Dexter had no gloves on, so his fingerprints would've been all over the plastic the body was wrapped in. This is a mistake an actual forensic employee would've never made, much less a serial killer, even in 1991.