The only difference between the A code and C code cars is a 4br carb/intake and flat top pistons that upped the compression. The intake will likely be "C6OE-9425-B". This is the engineering year, NOT the date stamp. You'll have to check that too. That will be like 4D11 which stands for 1964 April 11th. You have to compare that to car's date which you have. It should be about 10-20days before the car. Out to 90 days is acceptable, but less unlikely (you can't go after the car's build date, they didn't sit waiting for engines). The date on the heads (under the valve covers) should be near that on the block (behind the starter) and the intake. Things start to get tougher after these 3 big parts. The block's casting number should C6AE-6015-C which also is under the starter.
Let us know what you find.
