A 400 HP 318 would not be street friendly at all. Can a 400 HP 318 be built, yes but not by the average guy.
I'd be willing to bet most 340's and 360's on this forum aren't making 400.
FWIW my 383 powered 67 Fastback was running mid 11's at a buck 14 in 1980.
It was far from street friendly in race trim, it was my daily driver, I'd swap the cam and put on the slicks and go racing.
4.57 gear was good for the street and strip. lol