421 Super Duty 1963

Just aquired a 421 SD Pontiac Block, matching Crank, Rods w/ pistons, rebuildable. Anyone know of a site to run numbers on old Pontiac Blocks? I'm sure it is one of the nascar superduty limited production engines from 1962 or 1963.

Pontiac blocks are easy to identify if you know what to look for. It is simple, for example, to visually categorize all 1959-and-later blocks into 389/400 or non-389/400. All displacements other than 389/400 possess a "transfer lug" (found at the rear of the block shaped like a "mountian" or "pyramid"). There are only two exceptions: the 1961-62 421 SD (the same blank casting as the 389) and the 1973 SD-455. All V8 blocks cast prior to 1959 (287, 316, 347, and 370) were "standard" displacement and did not have a transfer lug. In addition, these 1955-58 blocks did not use side-mounted motor mounts as did all blocks from 1959 forward. All blocks through model year 1963 have a production number cast into the passenger side of the block. The casting number for these blocks are as follows:

1955 (287 c.i.d.) #518037
1956 (316 c.i.d.) #521560
1957 (347 c.i.d.) #523293
1958 (370 c.i.d.) #528456
1959 (389 c.i.d.) #532000
1960 (389 c.i.d.) #536387
1961 (389 c.i.d.) #538181
1961 (421 SD) #538181
1962 (389 c.i.d.) #538181
1962 (421 SD) #538181
1963 (326 c.i.d.) #548211
1963 (389 c.i.d.) #543680
1963 (421 c.i.d.) #544988

Thank You for the info. I did not know about the pyramid thing. I did find what i really have- YK, B-Body, 1965, 421, 376HP, Turbo 400, 4 Bolt Main, 3x2 BBL, High Output. Block code 9778791 (YK stamped on front), Last digit by distributer-hole is a "4". Motor mounts have two bolt-holes and two freeze-plugs ob each side. Thanks for new info. Regards, Rick