With those pistons, you can, with the right heads, make a lotta pressure;
which means you can run a big cam with a late-closing intake;
which will move the power peak to over 5000;
which with an automatic, will want to be shifted maybe 600rpm or more higher;
which, will require balancing so it doesn't vibrate itself to death.
Balancing is the last thing to do, even after working on the rods. External is fine for a streeter. Whoops, lemmee rephrase that;
IMO, external is fine for a streeter.