Help with BBC casting and stamp code

[Dan Almashy]

My firend just bought a used BBC from one of my other friends, after I introduced them, well one question is the engine was purchased as a 427, we are questioning now the codes, it has a block casting number of 6 numbers, 390406, the stamped pad is also weird with 09328360 and the letters ANOR...nothing in any of the several code books we have can verify these. even online sources have been checked. Could this have n=been a marine engine? or maybe a GM parts block that had been build by an independent? Thse stamoed numbers could be a GM parts number? Anyone have any ideas???