Playing with the tune-up specs (base timing, etc.) might yield a bit more off-idle response, but as I recall, those engines were about where they needed to be, as built. If you want more "top end/passing gear" power, then the 4bbl would be the upgrade to do, plus 2.25" dual exhaust.
The 340 cam will be dulled a bit by the smaller valves in the 318, though. Smaller valves due to the smaller bore size, although the DC LA Race Manual lists how to install the larger valves and such (probably more money than it's worth on a street car!). I believe the car would have a 2.93 rear axle ratio, with the TF904 trans. The 904 takes less power to run than the 727 does, which lets more of what you have get to the road, BUT it might need some friction upgrades to live with more power, by observation, as mentioned in some HOT ROD Magazine articles back then, related to drag strip longevity.
For "more power", substituting a 360 in place of the 318 would be the best incognito route. Add an Edelbrock Performer intake with some sort of Edelbrock 4bbl or a Street Demon carb . . . plus the dual exhaust mentioned above. BUT all of that costs money and where do you stop spending money.
Play with the tune-up items and try to improve off-idle response a bit, but don't expect anything really significant out of it. But any little bit helps . . .
Enjoy!
CBODY67