Small block gas mileage DD magnum/LA ?

I don’t see why not. I didn’t have headers on my ride, just the stock exhaust manifolds. No overdrive. LU? Yes.
The best mileage getter was the 4bbl. running and tuned very well, followed by the MSD. (When Working.)

3.23’s X .69 OD ratio is 2.22. Hummm. That should work well @ 80.
(When working) That's funny! (but true) LOL