I have 1963 Impala and this is the number I found on the block (3959532). I did look online to see what engine size that was and it said a 283. But i am confused becauses I have had others tell me the engine I have is a 327 just by looking at it with certain items it has. Can any one help me or send me pics of a 283 and a 327. Thanks.........
by the way I found the number near the firewall & distributor under the throttle body bracket.......

 

a 327 will look identical to a 283, the only way to tell the diference is the casting numbers and u did that, so u have the answer