How many main bolts do the LS1 5.7L blocks come from the factory with? I've heard 4-bolt mains and I've heard just 2-bolt mains but not really getting cut and dry answer from other folks I've asked. I'm debating on whether I can use an older re-buildable block or I'm thinking of getting one from Summit Racing that has the 6 bolt mains. Thx.

 

Stock is 6-bolt, 4 vertical and 2 horizontal (sides).

 

If I'm not mistaken, all Gen III/IV/V blocks have six bolt mains, in the configuration mentioned above. Only Gen I and II had the 2/4 bolt mains. Most times, buying an already machined block is cheaper than paying to have a block machined.