Differences between a Euro and U.S.spec 308?

For anything 1980-ish or after you can use the 17-digit VIN.

For the 1973-1977 US 308s they should have things like:
1. an air injection system with dual air pumps
2. insulated headers/exh. pipes with a thermal reactor muffler
3. a fuel evaporation control system
4. dual distributors
5. rectangular front and rear side marker lights ("Euro" are a small round style in the front fender only IIRC)
6. ugly bumpers
(not a complete list, but things like inner door reinforcements aren't typically "modified" by the Owners)

For the 1978-79 US 308s same list as above but:
1. only 1 (larger) air pump for the air injection
2. same insulated headers/pipes, but with cats and an insulated muffler

My guess is that you'll have more trouble with the US cars being "modified" rather than someone trying to pass off a Euro as a US version. If you really get serious about a particular year/model give me shout and I'd be glad to email you .pdf files of the OM for the US and Standard versions from the Owners Site (I'm assuming that you don't have access to them now).

PS You can't at least add "location" to your Profile "Mr. Carson"?

 

What year are you looking at?
Also, when Steve was talking about "ugly bumpers", he was saying the US version bumpers (front and back) stick out way to far for the design of the car.