Whats better a sbc 400 or a sbc 350 i wanna kno which one i should put in my car i have both the motors

A 400 is ok for about 500 HP, i have seen them go further, way more than that, but that is safer in the 550 HP range. More cubes, more better. BUT, the 350 1 piece rear mane seal can be bores and stroker to 396 or more cubic inches. I like the 1 piece rear mane seal blocks better. They can take TONS of abuse and i have seen them go .080 over bore several times. Not to mention, if you crack a 350 block, there is another one laying around somewhere and you can just swap the parts.

You crack a 400 block, you have to go out of your way to find another one and i have friends that have gone thru 3 blocks before finding one that wasnt junk.