engine codes

I'm trying to determine the engine code on a recently purchased 74 911 Targa. I was told the engine was updated by the second owner who brought it from Europe. The car has a rear deck lid with a "tail" and the inscription "Carrera 3.0" The engine number is 666 0006. Additionally my brother has a case he has held on to for several years with the engine number 655 0462. What is a 655? I've looked in all (limited) of my books and can't locate what this case belonged to.

In addition to the serial numbers you have given, those engines also have a 'Type Number' stamped very close, usually closer to the flywheel on a vertical surface. The type number will give a lot more information than the serial number!

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Warren Hall
1973 911S Targa