More compression, more valve shrouding with bigger valves. Likely no improvement. Better to deck the stock cylinder head to reduce CCs that way. Better to put lumps in with 1.84" intake and 1.6" exhaust. Bowl work, intake flashing cleanup, and polish on the chamber and exhaust helps too.
IntegratedJ has had luck with a Dualjet he just put on an integrated Varajet head, the Rochester 2G is better than Monojet even on stock intake. A HD 292 exhaust manifold with a 2.5" exit is a cheaper improvement too, or Langdon's Stovebolt cast headers with water heat (or if you have a truck there are headers available).
