383 400 engine I.D.

[bigmanjbmopar]

How would I know if my block is a 400 vs a 383? What pad stamp number / letter combos would I be on the look out for?

 

[IQ52]

The number cast into the left side of the block below the cylinder heads will tell you. 1851729, 2120329, 2468130 are 383 blocks. 3614230, 3698630, 4006530 are 400 blocks. There should even be 383 or 400 cast into the side of the block also.

 

[red 69 runner]

it should be stamped on the flat pad near the distributer,may have to scrape some paint off to see it