340 vs 340.
Decades ago Direct Connection had a list of their performance big block cams and ET results in the same 400 engine. Don't know where to find it. The differences were small increments, but improved as the cams got bigger. I don't recall the steps being much more or less than .10. (No radical, race only from what I remember.) But your "port cleaning" may overcome that. The lower first gear would also be an advantage as long as it didn't cause more wheel spin and the engine had a torque curve that would recover better from the 1-2 rpm drop.
Here ya go, Loco