You can make serious power with any of these. Sure, LSx platform puts up good numbers and you get EFI to boot. If starting with nothing, then LS crates are good options. However, you can still build a solid SBC or BBC for similar money minus the EFI. Typically those will be built with all forged internals which isnt' the case with LS crates.
I have a big investment in BBC stuff so that is why I'm sticking with that. I love the LS stuff but not enough to eat a huge loss. I also love the BBC sound :-). Not to mention so many people are dumping new BBC and SBC stuff now just to get on the LS bandwagon that you can get some really good deals. On the flip side, don't try and sell any SBC/BBC parts in this market
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John