1. Raise the compression. Your LPG pistons are a good beginning, and milling .050" or so off the head will help, too.
2. Install a relatively short-duration, high-lift cam. These are usually advertised as "RV" or "Pulling" cams.
3. Equal-length headers with LONG tubes. I like to figure out the volume of one cylinder, and make the header tube long enough to have the volume of the cylinder in the tube before it enters the collector. This takes some pretty imaginative plumbing to get all that pipe routed sometimes. Splitting the manifold and installing dual exhausts makes it a little easier. Make sure the length of pipe from each cylinder is the same. Trying to do this on the intake isn't very effective, because of the siamesed intake ports. A 12-port head helps, but that's a BIG-BUCK option!
4. Installing the cam slightly advanced from its "straight-up" position increases low-end torque, with a corresponding loss of high-speed horsepower.
Good luck!
Jerry
