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The block and just about all parts have a "casting number" on them. Your block #3970010 was used by GM from 1969 through 1980 in anything from a 1/2 ton pickup, to the HOT Z-28's. It could be either a 2 bolt or a 4 bolt design. What that means is that the crankshaft is held in the engine block by main bearing caps that are designed with either 2 bolts or 4 bolts. The 2 bolt is good for non-high performance, less than 6,000 RPM's. The 4 bolt design, spreads the rotational stess over a much wider area within the block is used for over 6,000 RPM's. Hope this helps.

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15y ago

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