Olds head #'s
 Year              Engine    CC's     Casting#                   Notes 1                  
 '64                330                     385101                      Used ROCKER SHAFTS rather than pairs on PEDESTALS. 2  
'65                 330                     ??????                      All V-8s now using PEDESTALS. 3                 
'66                 330          60        394497                  
'68 - '69         350          64        397742                      Excellent candidate for use today. Good flowing, and high compression. 6                  
'70                 350         64         403859                      W-31's had larger 2.000 intakes. '69                                                                                                    W-31's? 7                  
'71                 350         64         409147                      W-31's had larger [2.000] valves. 7A               
'72                 350         64         409147                      The 'A' is a subscript, like ¼" tall, to lower right of the '7', like | 7A. 8             
 '73 - '76        350         79         411929                       Smog heads. Have huge bb-sized 79cc chambers yielding poor compression ratios  without extremes of compensation. 10 
            
'76                 260         57         550362                        2A             
'76 - '81         260                      554715                        Easy way to ID a 260 engine. 3A             
'77 - '80         350         75         554716                        1/2" bolt holes. 4A             
'77 - '79         403         83         554717                        Matches the 4A or 4B block, get it? Easy way to ID a 403. 1/2" bolt holes. 5A  
'80 - '84         307         64         3317                            '85 also??? 6A             
'85 - ??          307         67         5844                            Non-ECM Canadian cars? 7A             
'85 - '90         307         67         0142                            This 'A', and the others from 2A to 6A, is a large capital letter equal in size to, and immediately adjacent to the 7, like 7A.

D3A               350                      3948                            Diesel.