Auto Parts: 283 Crankshaft I.D., harmonic balancer, crankshaft

Question
Mike,
 The crankshaft in my 1964 283 cu. in. engine is numbered GM2 3849847 with a completely round flange for the flywheel. I looked at a crankshaft today for my engine, it is numbered GM4 3849847 also BUT the flywheel flange is not completely round, there is a small "V" notch cut into the crankshaft flange. One I.D. book I have shows the "V" flange to be for a 302, yet the casting number says it is for a 1963-1967, 283. Could the notch have been for balancing purposes??? Also what do the prefixes GM2 & GM4 stand for??? Do they indicate month, day & year. Bottom line is I would like to use the GM4 crank in my 1964 block, #3849852 instead of the GM2 crank. Would it work??? Thanks Mike.
Al

Answer
    There shouldn't be any problem.  I asked a couple of guys I know who have a little more experience running a machine shop and they said that the casting number is all that they go by.  That said, they also warned me that a lot of older cranks were subjected to machine work without being marked as such.  So, you should be able to use either crankshaft but they should be miked to determine journal diameters, and the block miked as well.  A good job with the micrometer will save a lot of headaches later on.  If you can afford it, balancing the rotating assembly after you have the rods, pistons, flywheel, and harmonic balancer would be a real good idea.  You would be surprised at how much smoother a properly balanced engine is than one that is just put together with equal-weight parts.