The links in this thread are a good place to start.
http://67-72chevytrucks.com/vboard/s...d.php?t=736001
Things like THERMAC, PCV, and to a lessor extent the charcoal canister are actually useful and beneficial.
If it is tuned for sea level, tuning for your primary altitude is a good place to start.
If the converter is one of the pellet type, switching to a better flowing honeycomb type can gain some performance.