Jim,
From everything I've read the Mexico block is the preferred block. The mains are supposed to be heavier and the cylinder walls are thicker, I also read on the HAMB that the block has more nickel in it which is said to make it more durable. The engine I'm building is a 1980 block.

~ Craig
1958 Viking 4400
"The Book of Thor"
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1960 Chevrolet C10
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'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)

If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane