408 SB versus BB 541

You can build a 470 or 500 ci with a 400 block. 550 -700 or so HP. easy 10 sec 1/4.
the low deck will provide better header fit in an A-body. plus it will be a tad lighter engine.
and if you gear it right and get the suspension up to snuff it could go 200 mph.
It's easy to build a death ride, I would get the chassis up to snuff before putting the HP to it.