To take this further the GTLs had different front rear screens, the front is higher and rear I s completely different plus less overhang past the rear wheels. As William mentions only the GTLs had the chrome sill strip but owners’ retro fitted it hence the black series 1 above. Also to my knowledge only GTLs had the 2 screw heads on the headlights surrounds, although there is a well-known GT in the UK that has this, as the owner told me he couldn’t work out how these fitted on, as the original studs had been sheared, by the time he got hold of them.
The easiest way to tell if a car is a series 1 or 2 GT is to look at the dashboard, series 1 had 3 separate indicators whilst series 2 had a single triangle moulding incorporating the 3 lights. There many other differences as Dave can tell you.
The only other oddity I have is on this tread
http://www.lancia.myzen.co.uk/forum/index.php?topic=7604.0 which looks like a frontend rebuild. I have also seen a few customised fronts, including a Ferrari-ish nose and the blizzard loraymo inspired convertible which has been for sale in the US for a number of years
http://www.lancia.myzen.co.uk/forum/index.php?topic=5850.0 
