First thing is to verify the ignition timing is correct. Yes, the 383 2bbl with 2.76 rear gears will lay some rubber, just not a giant smokey burnout. But will respectfully raise the nose as it leaves, too. The stock (1800rpm stall, or thereabouts) converter is needed as it is "tight" for best highway fuel economy. Tighter than similar Ford or GM cars, with better off-idle throttle response.
At your altitude, you can add another 2 degrees BTDC to the OEM timing setting, which can compensate a bit for your higher altitude.
Of course, do you have the EFI configured to control both the mixture and ignition timing? Or just the mixture?
Personally, I would expect the EFI to have very sharp throttle response off-icle. Perhaps you need to contact FiTech for guidance.
Yes, the car is "heavy", as our '66 Newport Town Sedan 383 2bbl has a title weight of 4100 lbs, being probably closer to 4400lbs "wet with driver"? When the car was new, it was credible in performance, but with only about an 80mph 1/4 mile speed for the 383 2bbl. 383 4bbls and 3.23 gears were quicker and faster.
The OTHER thing is . . . from a dead stop, only punch it about 1/2 throttle initially, to get things moving, then at about 25mph in low gear, go the rest of the way to WOT and the higher 1-2 shift point. If you try to go immediately to WOT, it WILL bog the engine and lose any vac advance in the distributor at the lower rpms. By observation, the 383 2bbl distributors had a pretty good advance curve in them, from the factory, usually with a total of about 36 degrees of total advance.
So contact FiTech for any tweaks to the program and then learn to drive the car to extract its best acceleration performance.
Enjoy!
CBODY67