Street build. I have 4.155 good bore 511 sbc 400 block, 2 cranks. A 350 eagle steel, and a stock 3.750 400 crankshaft. Have 400 and 350 rods. And flattop 377 / 406 pistons. . Heads are Dart pro 1. 230cc. 64cc chamber. Would like to run pump gas. Can go.e85. Perfer pump 93. . So ? Is destroke. 377. Or stock crank, rod, cast flat top piston 406. Do have some shitty 882s dont want to use. Also have a scatt ultra lite 3.875 crank could build 421. And another 400 block..a few 30 over 350 blocks. . Im rhinking 377 with dart heads. For good flow, decent rpm, 500hp plus. Street. 93 pump gas. Ok lets here it.

 

Why not go with the 421!

I say no to the stock 400 crank.

Not sure if your 3875 crank is 400 mains or 350 mains... but of course you would need spacers and line bore for the 350 crank... not that it's bad, part of the process is to get some splayed 4 bolt mains machined at the same time, as that can run at high RPM with very good valvetrain, little bit like the formula for NASCAR in the early 1980's.

With Performance Trends Engine Analyzer, look at a few different combinations.

 

All I'm going to say is the 421 will get you to your goal a lot easier than any other combo... so why not?

 

You say "street" build....how many miles a year will you drive it? Will it be mostly flogging it from stoplight to stoplight, will there be any interstate driving/long to longer road trips? Basically, how is the car going to used 95% of the time? What transmission and rear-end/gears will be behind it? Fuel induction/system/supply? These factors should most certainly point you to the right combination! For what it's worth, my uncle builds engines for everything from numbers matching Hemi Super Birds to late-model race cars, he has a waiting list two years out....when inquiring with him about a similar build for the street, his advice was with today's pricing, technology, parts availability and resources....go as big (cubic inches) as you can (obviously within reason, not talking about needing a $3k-$5k block as a starting point)....he says it's almost the same money to build a 350 or a 400+ sbc these days....and the guys who keep it a 350ish wish they did a 383, and the 383 guys wish they did a 406 and the.....the decade's old saying 'there's no replacement for displacement' is truer than ever with all the parts available in 2023!!!! But like I asked, it all depends what conditions you plan on running your engine under on a regular basis!? Do you want a tire shredder or a Bonneville Salt Flats missile, or something in-between!?👍