Efficient as in power?
For power - I have very little expertise here (but I'll blather on anyway). I'd do a chip, brand new battery (perhaps a lithium one), synth oils & lubes, short diff (like a 4.27), shorter wheels, remove weight, eliminate vac leaks, maybe install bigger injectors, WBO2, install a better flowing catalyst, pick up cold air for intake, remove throttle body heater, colder thermostat, replace engine driven fan with electrical unit, thin out the coolant & add a surfactant like "water wetter." You might get 25% more power with these mods.
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Dave.....those are a lot of things for power, and all great. I just have 2 words.....LOL....Stroker Motor
Cheers,
~Ralph