Just recently brought in a Restored C3 and in the process of another , it all depends on the year models ( and this makes a huge difference ) you should be extremely careful with OS sellers unless you have a good relationship with them or have someone who can view the car for you.
Original ( and who really knows to what extent matching numbers goes ?? ) - what really is Original these Days ?
You will pay the price for the smell of Original
Here in Australia you can pay over inflated prices for some C3 ( from 74 - early 80s ) but the Car will have been imported and most cases have rego for you , but you will pay .......$$$$$ , Also in Australia sellers are asking the same prices for 74-80s as what you can get for a solid 73 C3 in USA , but you will need to do the import.
Be careful with Cars on the East Coast ( Snow and Salt )
If you chance your arm and look at the many sites available you can grab a bargain but it comes with risks ! ( so many sites outside of EBAY )
Get to know good shipping companies as well ...... bringing in a Project Car will cost a lot so be prepared for New Paint , Interior , Rust Issues ,suspension , brakes etc..
My advice if you can buy local ( and at a reasonable price ) go for it ... and know the value of each year model from 68 to early 80's ( its vital )
Good Luck , I am sure the other members will chip in with their own stories and experiences :o)