Cool! Keep us posted on your progress!
A true spread bore two barrel that is readily available is the Rochester 2SE. It was used on the Chevy S-10 and Jeep Cherokee's that ran the 2.8L v6.
The pattern is pretty different. I'm not sure how you would make it work other than going aftermarket intake and build your own carburetor plate.
If you look into the Rochester, be careful not to snag the E2SE. It is a computer controlled version that was used for three years or so while GM was shifting from Carburetors to TBI. It allowed them to meet the emission requirement short term and bridged the gap.
It's not that the E2SE isn't a pretty good little carburetor, it's all the other stuff that would be required to make it work.
Some of the Japanese carbs could also be made to work on your slant. Similar issues would poke their noses up though.
Mainstream would be to go with the Holley 390, but you're going to want a bit more compression to make things work. The 4bbl will get you into the 23mpg range, but an extensive recurve would be needed for the Distributor.
Some folks have run the Holley 2300 series to good results. The 350 cfm model is just about right for a street car. The 500 cfm is a drag race only item that needs extensive engine mods to work well with the Slant Six. My Valiant launches harder with the 500 cfm 2 bbl than any other carb I've had on there.
Mid 20's with the 350 cfm. Not as many mods required to use it. The Offy, Clifford, or Aussie intake manifolds would be the trick there. Best for lower RPM torque would be the Offy in my opinion. Smaller runner cross sections. Top end would be the Aussie. The Clifford sports carb heat for Header applications and can deliver good numbers on both ends of the spectrum.
Another option is the Weber DGEV or similar. It gives you progressive, and there are manifolds out there for it. It's on the smallish size for the displacement, but should give terrific throttle response, and good road power. At the strip your going to run out up top, but that shouldn't be a concern with the build your talking about. I think Lynx makes the intake manifold for it. They also make manifolds for single, double and triple DCOE's, a dual DGEV and various configurations of SU carbs. (Which once you get used to the tuning procedure, aren't so bad, just not readily available on this side of the pond.)
HEI is really going to give you a better burn. I'm prepping to dump my Mopar EI this winter once the racing season is over.
For a clean burn, multi-spark boxes can't be beat. The Mallory box is a bit less money than the MSD, and works fine. Move the coil from the stock location on the head onto the fender. Look at an aftermarket coil choice. There are a lot to choose from, just make sure you match the coil, distributor and EI to an appropriate Ballast resistor. Not all parts play well together.
Too bad your half way across the continent, or we'd get you in the driveway and get busy!
CJ