Okay, here's my 2 cents. If you're looking for low end, you want torque. I'm assuming you have an automatic transmission, I'd suggest you consider a looser torque converter, in the 2400-2800 range. That will multiply the torque to near double what the flywheel develops, allowing faster off-the- line performance. Any looser than that will cause excessive slip at highway speeds, unless you upgrade to a later model trans with a lock up converter. It is possible to have your 727 transmission rebuilt with lower 1st & 2nd gears to give you more low end grunt.
A750 carb sounds like overkill for a street car, the primaries are too big to provide decent part throttle response. Great for top end power, less so for low end grunt. For a 383 it's a tad too big, unless your goal is top end screaming on the dragstrips and highways. Same goes for a 3" exhaust. 2.5" duals is just fine for a street car, for low end response you want some back pressure on the pipes, and it won't sacrifice gas consumption or that nice musclecar idle we all love.
Speaking of idle, you never did mention what kind of camshaft you have/intend for this.
Back to the original post: LSD vs Spool. For a street car with limited track time, I vote LSD. Easier on the axles & tires, not to mention gas mileage. Manuvering around parking lots, corners and curves with a spool fighting you will require more power to push it thru the curves, requiring more throttle and gas.
You got 275s mounted under yours? Damn, I'm envious! What kind of rims and backspacing are you running? Post some pics please! That's a lot of traction, add a spool and see your gas mileage dip into the low single digit range as your 383 fights to push it around a corner. Seriously, limited slip please, before you buy some Arabian prince another Bentley or a fleet of Tesla's for some oil executive team. Your wallet and the ecosystem will thank you in the long run. Spend a little extra coin now and save it back in the long run.