Quote:
Originally Posted by bigblockv6
The only one that's good on identifying the year of a V6 by the serial number is Lewis Matkin. Otherwise look at some of the casting dates on the intake manifold and exhaust manifold, if original they will give you a close ball park figure of what year the engine is. The 305C was manufactured from 1960-74 not 60-61.

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BigblockV6, This brings up an interesting point. If I look at a Motors Manual for our vintage of trucks I see that the letter on the engine codes changed from year to year. My 62 has a D block, previous had C and subsequent years had E models. Did GMC just use blocks from inventory willy nilly or was there some sort of sequence in the letter changes and use of the block.
I sort of always assumed that the letter changes followed the years of production, appears that is not correct.