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PONTIAC BLOCK CASTING CODES
See Date Code Below
Casting # Year CID HP Main Notes
518037 1955 287 173, 180, 200 2  
521560 1956 316 192, 205, 216, 227, 285 2  
523293 1957 347 227, 244, 252, 270, 290, 317 2  
528456 1958 370 240, 255, 270, 285, 300, 315, 330 2  
532000 1959 389 215, 245, 260, 280, 300, 315, 330 345 2  
536387 1960 389 215, 230, 235, 281, 283, 303, 318 2  
536387 1960 389 333, 348, 363 4 SD
542426 1961 389     SR
538181 1961-62 389 368, 385 4  
538181 1961-62 421 373, 405 4 SD
548913 1962 421 405 4 SD (late)
543680 1963 389 215, 230, 235, 267.-283, 303, 313 2  
544988 1963 421 320, 353, 370 2  
544988 1963 421 390, 405, 410 2 SD
548211 1963 326 250, 260, 280 2  
9773153 1964 326 250, 280 2  
9773155 1964 389 215, 230, 235, 267, 283, 303, 306 2  
9773156 1964 326 325, 330, 348 2  
9773157 1964 421 320, 350, 370 2  
9773383 1964 389   2  
9773384 1964 421   2  
9778789 1965-66 389 256, 290, 326, 333, 335, 338, 360 2  
9778791 1965-66 421 338, 350, 256, 376 2  
9778840 1965-66 326 250, 285 2  
9782611 1966 421 338, 350, 256, 376 2  
9786133 1967 400 255, 260, 265, 290, 325, 335, 360 2&4  
9786135 1967 428 360, 376 4  
9786339 1967 326 250, 285 2  
9787840 1967 326   2  
9792250 1968 400   2  
9792506 1968 400 335, 360 4 RA
545887 1969 400   4 RA5
546313 1969 303   4 RA5 short deck
9792506 1969 400   4 RA4
9792968 1969 400 375 4 RA5
9790071 1968-69 400 265, 290, 330, 340, 350, 366 2&4  
9790079 1968-69 350 265, 320, 325 2  
9792968 1968-69 428 360, 370, 375, 390 2&4  
481708 1970 400   4 RA5
9799140 1970 455 360, 370 2  
9799914 1970 400 265, 290, 330, 350 2  
9799914 1970 400 345, 366 4 RA3
9799915 1970 400 370 4 RA4
9799916 1970 350 255 2  
481990 1971-72 350 175, 250 2  
483677 1971-72 455 200, 250, 280, 325 2  
483677 1971-72 455 300, 335 2&4 HO
481988 1971-74 400 200, 250, 265, 300 2  
485428 1971-74 455 200, 215, 250, 265, 300 2&4  
485212 1972 366   4  
487638 1972 455   2  
493482 1973 455   2  
490132 1973-74 455 290 4 SD
488986 1973-76 350 150, 155, 170, 175 2  
488986 1975 400   2 early
500557 1975 400   2 late
500810 1975 350   2 late
500813 1975-76 455   2  
525934 1977 301 135 2  
568557 1977-79 400 180, 200, 220 2  

Date code letter deciphering:

The date code is 4 digits. The first digit is the month, the next 2 digits are the day of the month, and the last digit is the year (6 could be 1966 or 1976).

A=January

B=February

C=March

D=April

E=May

F=June

G=July

H=August

I=September

J=October (September for 1967 model year)

K=November

L=December

M=December (1966 Only, for 1967 model year)