One of the cool things about a 67 is the trim tag can tell you alot about the car. 4P - L48, 4N - L35, 4K - L78, 4F - remote mirror (is it on the car?). You did not provide any info on other equipment the car has. So, unless the seller has some real factory documents to back up his claim, this car is almost certainly not an SS.
If the car is a Canadian model, GM of Canada can provide documentation as to its original build equipment.
[This message has been edited by Ed Ernst (edited 09-26-2001).]