I have a 350 currently being disassembled in the car and a 400 about to be put in temporarily. I'd like to add boost in about a year (Financialy speaking). The 400 is a production block, and the 350 is a 1987 block. Either way I go, I'd like to destroke it, with like a 327 crank or something. Would it be worth it to get a high performance 400ci block, the "Little M" that's like $1800? Or would I be just as well off building up the 350? I plan on O-ringing the block.

 

I have a few 400's some people warn or cry about using 400 production blocks. the advantages of using that 87 block are many; the roller cam provisions, the one piece rear main seal, its inherent strength of the casting (especially when splayed caps are used) if you are planning on building power above the 600 range I would recommend the aftermarket block. O-ringing is very needed on fords but the chevrolets having the better clamping ability a felpro loc-wire head gasket works very nice exept for full effort race motors with obscene boost but even they blow the gaskets when real o-ringing is done on massive boost or nitrous applications. now the 400 if used with the TD girdle, ARP bolts, and a blockfill to below the freeze plugs makes a strong large cube engine. a factory style GM 350 steel crank can handle alot of power. there is a guy that races an blown 1100 hp rail locally that only uses race prepped factory 1053 steel cranks in his motors. this in your 400 would yield 377 (.030) and 383 (.060). dont let people tell you that .060 is too much, it doesnt over heat, break, or any of those other old BS tales. just make sure your machinist does a sonic check to make sure that the core shift from the casting process didnt leave the walls thinner in one spot than another.