Better ignition is cheap and will improve both performance and mileage, while reducing emissions. You can then increase your spark plug gap to 0.060, which allows you to run leaner. Lookup the HEI posts, which gives better spark than the Mopar electronic. Next would be more aggressive spark timing. You might try 15 - 20 deg BTDC at idle. Insure you have the "high mileage" vacuum advance, which uses the inner hole (bent arm, "8.5R"). Downside is more tendancy to knock (going uphill in 3rd at high throttle). You can install a GM knock sensor to monitor that. By the time you hear it in the cabin, it is too much.
A turbo will give you more power, with minimal loss in mileage at low rpm. Some claim it will also improve your mileage, but I don't see how. If not at WOT, any boost energy the turbo recovers is just dissipated by the throttle plate. A diesel has no throttle plate, and thus uses the recovered energy. That is why a turbo-diesel is a wise design, and most use that. A turbo slant is neat, and the best way to overcome the restricted breathing, but there is no store-bought solution.
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