67 dart gts 383 cylinder heads??

I have owned 3-67 Dart GTS's so I can talk about them. All came with the "516" closed chamber small valve heads and short runner intake with 580 CFM carb. Adding the 915's and a later intake or aluminum intake with a larger carb definitely woke one of them up! Best I ever did with the stock combo (4-speed car) was 15.50 at 90 MPH but when I put on the 915's, stock 68 301 intake, and 650 Carter it immediately went 14.91 at 102 MPH but the tires limited the traction. I never did much more with the combo but seat of the pants feel was MUCH better!