Sounds like you already have some ideas. Make the intake ports on the head rough. A 40 grit sanding roll will make an improvement. The Singh groove will allow higher boost and more ignition timing without detonation. More timing may or may not improve mileage. For oil I use 1 quart Mobile 1 5w-30 and the rest Motorcraft 5w-30. Use the largest filter you can fit behind the radiator.
Drill a small hole in the distributor cap opposite the vent, the hole about the size of the plastic emissions hose. Epoxy a piece of plastic vacuum line into the hole, and run that line to the throttle body. This will draw the ozone from the cap to the engine where it can enhance combustion.
On the exhaust manifold, there is a big protrusion in cyl #3 that is your biggest enemy. Your second biggest obstacles are the bumps in the back of cyls #3&4. Other than that, gasket match the ports and it will work well for you.
While you have the head off, round off all of the sharp edges in the combustion chamber. Don't just take the sharp edge off, actually radius these edges. The smoother the transition, the more power you make. If working with a 782 head, open up the double hump a bit to allow more flow past the valves.
Though not related to having the head off, inflating tires to about 40 psi
can make a noticeable difference without compromising handling too much.
If you contact me, we can chat on the phone. I seem to remember stuff better with somebody live talking to me. You can also jump on the www.mpgResearch.com
forum for more ideas.