You want bottom end grunt so the mileage is supreme. I would tie in 1-4 and 2-3 with a cross-over to each. This helps stop the pulse and little back-pressure is captured for the lower bite. You have wide open pipes and that is more or less a free flow WOT of air flow. But if you are just sporting around with that low power classic, you would gain a lot of bottom if you aim for a little back pressure or more stick to the lower rpm range of that street pipe.

Say even if you did occasionally hit the drag strip, you wouldn't loose to much HP short of building a whole new pipe for the 1/4 mile.