Casting numbers say which part a block or head is; the stamp and date code say when and where the engine was built. Start with the VIN for what the car left the factory with, then check the engine itself, since engines get swapped.
| Casting | Years | Cubic inches | Main caps | Notes |
|---|---|---|---|---|
| 3902406 | 1966/1967 | 396 | 2 or 4 | Second-design 396 block. |
| 3916323 | Mid 1967-mid 1968 | 396 | 2 or 4 | |
| 3935440 | 1968-1969 | 396 | 2 or 4 | |
| 3955272 | 1969 | 396 | 2 or 4 | |
| 3963512 | 1969 427; 1970-1976 454 / 1969-1971 | 427, 454 | 2 or 4 | Not the same as small-block 3959512. |
| 3969854 | Late 1969-1972 | 396 (1969), 402 (1970-72) | 2 or 4 | short-tower distributor boss; casting date on top of the bellhousing flange near the casting number. |
Many castings were used for more than one size, so measure the bore and stroke if in doubt.
| Casting | Years | Used on | Chamber (cc) | Valves (in) | Notes |
|---|---|---|---|---|---|
| 3964290 | Late 1969-1970; CarTech: small-plug 290 castings 1970-1976 | 396, 402, 427, 454 | 101.0 | 2.06/1.72 | oval port, closed chamber; Changed to the small tapered-seat ("peanut") spark plug; early castings had the standard plug. CarTech: largest as-cast oval intake port (NHRA max 262 cc). |
| 3964291 | Late 1969-1970; | 396/375, 402/375, 427/425, 454/450 (LS6) | 109.0 | 2.19/1.88 | rectangle port, closed chamber; CarTech: largest as-cast rectangle port (1970 LS6). |
| 3994026 | 1971 | 454/425 (LS6) | 118 | 2.19/1.88 | rectangle port, open chamber; CarTech: 127 cc exhaust port, the largest factory iron exhaust port. |
| 353049 | 1973; 1973-1984 | 454 | 113.1 | 2.06/1.72 | oval port, open chamber; CarTech: largest oval exhaust port (NHRA max 119 cc), a pick for turbo builds. |
| 336781 | 1973/1974-1984/85 | 454 | 113.1 | 2.06/1.72 | oval port, open chamber; PASS marked |