FWIW

There are at least six different 3 digit ENG assembly numbers (actually 7 digit) for the '69 383 engine in a Road Runner.

1 - you didn't provide enough information for the correct answer
2 - the number is on the fender tag of a Lynch Rd. Detroit, MI assembled Road Runner (Do you have a fender tag? Where was your RR built?)
3 - the number is on the broadcast sheet (Do you have a broadcast sheet?)

Since there is usually not a lot of help offered to invent a broadcast sheet or fender tag, you probably will NOT receive a serious answer.

FAIR ENOUGH??