Is this engine builder nuts?

A 66 Dart might weigh 3,000 pounds, probably less. You don't need to port 273 heads, just clean up the bowls and get a good valve job, get some good pistons, bore and hone with torque plates, a cam in the 268 advertised duration and don't look back. Use a Q'jet, T'Quad, or AVS. Tune, Tune, Tune. You do not have room for big enough rear tires anyway, 273 or 318 let alone a 360.