The answer is , as streetable as you'd like, And this one sounds purposely a "docile" build. A few members here roam with such beasts , and they'll likely pipe up.
And then there's the old addage: " Run what ya brung son! ".
Welcome to Team Chevelle Steve! You may find 600 ft lbs to your liking, or simply too much. ( in my limited experience, I can no longer maintain traction at anything above 1/2 throttle on street meats using a race 850 Holley. Hoping a well prepped Q jet softens the hit some )
BTW, its not quite a 540 cubic inch engine. Around town smoothness notwithstandng, its a matter of fact that the bigger it is, the more it eats. Overdrive or not, your highway milage wont be good. And you may be happy with the 350/400 ft lbs of torque from a smaller engine, which would clearly need less fuel to "roam".
for a local hot rod.... spot on perfect! The epitome of diesel like BBC torque with out a blower or a shot!
Be careful man, its a HANDFUL! ( E.g with an old style but good suspension; can only hit it WOT when its "on a string" straight, or ELSE! )
good luck with your quest !