Had a Diplomat coupe years ago: 318 4bbl, lockup converter & OD, most likely a 2.45 gear, 235/70R15s. It was laaaazzy around town, but IIRC 75MPH was something like 17-1800RPM, and it was fine, even on small hills & headwinds. Something like California's Grapevine would have me either giving it some boot or pulling it down a gear.
For a carb I'd want a T-Quad for its small primaries, but why bother if your plans are to run the EFI/Turbo setup? With carbs, I get the best MPG driving with as little throttle as possible; 2 of my EFI cars pull better MPG at the lowest RPM they'll turn & still pull the car, which with a carb would man frequent large throttle openings & low vacuum to maintain speed. The 3rd (it's the least aerodynamic) gets better MPG @ 3000RPM than at 2700. Mystifying? Nope, aero.
My GMC 454 dually (5500 lbs, 4.10, TH400, Gear Vendors = 3.23ish gear) makes its max TQ @ 1700, but that doesn't equate to hwy speeds; 65-70 = 2700RPM. Needs more gear towing uphill, but unladen it's a freakin' locomotive.
Hopefully your turbo setup is sized right so it won't require much RPM. Seems like a really good application for a stroker motor.