You're quite welcome. "But Wait, There's More", haha...
Aero research on vehicles pretty much started with the Germans in the 1930s, and other sources for info would include an article by Car and Driver using a Dodge B-van, teh 2nd versionof the original '65 HemiCuda drag car, the Chrysler engineers' work with the Charger 500 & wing cars, early on in the TransAm series when they started drooping the noses, and later when the windshields were laid back a little and the upper cab subtly reshaped (Yunick's '68 Camaro) into a more fastback shape, drip channels set flush. That car & the Chevelle Cup car had a lot of underside fairing done, even with their creative ft air dam work.
A 3.5" rear spoiler at a 45 on the back of Melrose Missile VII picked up about 6-7 MPH and about .4 ET IIRC, though that was a 160MPH+ car on fuel at the time. Basically the car was spinning the rear tires from lift.
Bang for buck on a drag car like a '66-'67 B would likely be blanking off openings within reason, dropping the nose, and an air dam; reducing the frontal area would be nice, but a lot of work.