The best one I've seen to date:
Coming up on what looks like a Red '00 Cobra R (had the '00R rear wing) or a 03/04 Cobra (had the hood, front and rear bumpers, hood (if I recall), snakes on the fenders, proper side scoops, dual exhaust, etc. So I'm thinking ok, an 03/04 with a Cobra R wing. But still something wasn't right. All in all it was a pretty good job, except two things that stuck out when I got closer: flared out V6 rocker panels (hardest trim piece to get for 03/04 Cobra compared to the bumpers and hood) and, get this, a huge aftermarket 3.8 emblem where the GT/SVT emblem would be. There was no burble idling, and when he took off it was obvious it was a V6.
Most people would have bought it but I notice subtle things like the wrong rocker panels... or rolling up behind it, the lack of the 03/04 Cobra style black fuel tank cover, IRS, etc. And the IRS specific exhaust is very visible and obvious, hangs low, goes straight under the IRS, out to the side and back out the rear, no loop like over the solid rears, that is plain as day on a real IRS Cobra. And other touches like the spoilers/wind deflectors in the windshield wipers that nobody knows about except for serious SVT guys.
Most who do Fobra's usually mess up the rockers or the quarter side scoops, those are very specific to 03/04 Cobras and sufficient to identify real or fake from a distance in about .1 seconds. And a '00 Cobra R? Well lets just say that chances are you won't see a real one being driven on the street ever, there were only 300 made and most are in climate controlled garages or dedicated track toys.