350 carbs run #35 pilots and #75 mains, and 400 carbs were stocked with #40 pilot jets. I think the emulsifier tubes might be slightly different, too, as the part numbers are different, but I've never compared them side by side. But for all intents and purposes, they are the same. Oh yeah, 350 air screws were set what 7/8 turn, and 400 is 2 turns plus or minus 1/8 I think.
