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BLOCK IDENTIFICATION Continued
The block date code is found just to the left of the distributor hole at the back of the block. This can make it difficult to read if the engine is installed in the car. This code (B059) breaks down as February 5, 1969.
The block casting number on mid ‘67-and-later blocks is found just behind the #8 cylinder on the passenger side of the block. This number, 9792968, denotes a 1969 428. The number is located next to the distributor hole on earlier engines.
Non-389/400 engines featured an identification or transfer lug on the rear passenger side of the block. The exceptions to this were the 1961-62 421 Super Duty, and the 1973 455 Super Duty engines.
Many of Pontiac’s 2-bolt main engines, most notably the lower-performance 428s (1969) and 455s (1970-and-later), were drilled and tapped for 4-bolt caps from the factory.
Along with the displacements cast into the side of the block, additional identifiers were added to the lifter valley ribs as well. “28” denotes this as a 428, while “55” would reflect a 455 and “00” a 400.
Displacement identifiers for the 350 began in 1970, while all 1971-and-later 400s received the treatment.
Pontiac began casting displacements in the sides of the block (among other places) in the late ‘60s. This practice started with the 428s in 1968. 455s received the identifiers in 1970 when they replaced the 428s.
FYI: In 1977, only the 350 and 400 c.i.d. engines remained. A new 301 Pontiac short deck engine joined the line-up along with some other "corporate engines", such as the Olds 403 and the Chevy 305. The Pontiac 400 block was cast with revised motor mount bosses, and will only mount in late Firebirds or Grand Prixs. The blank casting number for the 1977-79 400 is #568557. The 301 can easily be recognized by the lateral oil filter location. In other words, the 301 oil filter sticks straight out, unlike other Pontiac blocks which are attached to a housing that aims the oil filter downward.

A wide variety of specific engine/trans codes are stamped into the front of production blocks. Trans codes may appear to conflict. Prior to 1965 (the start of the "two letter" system) the two digit engine code, which was the last two digits of the full six or seven digit part number, was stamped followed by the standard trans code. An optional trans code, if installed in the vehicle, appears nearby, often on top of the other characters. Most production blocks, except 1964-66 and most 1967s, received a vehicle identification (V.I.N.) stamp. Prior to 1964, the block V.I.N. was identical to the actual vehicle code. Beginning in late 1967, block V.I.N.s appeared with the digit "2" designating a "Pontiac" engine, followed by the year, a letter identifying the assembly plant, and the vehicle serial number.

A researcher familiar with the various assembly plant code letters can sometimes ascertain whether a block was originally installed in a Firebird or a GTO. Lordstown (U), Norwood (N), and Van Nuys (L) built Firebirds, but not Tempests. A block V.I.N. of 29L123456 would indicate that the block was originally installed in a Firebird built at Van Nuys, CA.