68-70 Manifolds on 72 340?

The cam is comp cam CL20-224-4, duration 274/286, lift .488/.499. It has an air gap also. When I did the car I thought I wanted as much performance as possible. I rarely use any of the power. I made this decision driving home from Carlisle on the turnpike going 70 mph at 3500 rpms for an hour.