Yes its the good number i checked it on
http://www.v8cars.hu/oldsvin/decode.php
and this is what comes out :
3K47H9M442280
Year: 1979
Division: Oldsmobile
Series: Cutlass Calais
Body: Coupe
Engine: 305 (5.0) V8 4BBL
Plant: Lansing, Michigan
Serial Number: 442280
So must b the good VIN number i guess...