Whats the deal with 340s?

I've owned much of all. I did a mild 340/360 comparison. Here is what I did and the results. Used the same 750dp Holley, same dual plane intake, same 340 J heads, same cam (MP . 280/.474), connected to the same 2400 converter/727 in the same 3300 lb Dart with 3.91's. I did replace the pistons in the 360 to get the compression ratio the same.
340 ran 13.60's
360 ran 13.30's
340 cost 200.00 for a builder core (good deal from a friend)
360 cost 25.00 from a dodge pickup on it's way to the bone yard.
No, not claiming this is all tale. Just reporting this experiment.