I went looking for 'blueprints' of the 'brick' and the first thing to show up was the M1715 Ambulance and civilian Gladiator ambulance, which has a raked windscreen, shown together.
While fuel economy for the M1715 was given at 7.6-mpg, at unspecified conditions, I couldn't find mpg data on the Gladiator.
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Today's Stellantis-JEEP Gladiator incorporates the slant-back screen, so that's a clue. Some owners of the diesel-powered JEEP are reporting over 30-mpg.
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It's possible that adding edge radii to the sides and top of the windshield frame ( header and A-pillars ) could achieve fully-attached flow around to top and sides ( like the '32-Coupe at A2 Wind Tunnel ).
Dr. Paul MacCready, of AeroVironment received a US Patent for an aerodynamic fairing for the JEEP 'Wrangler' windshield frame, which amounted to attaching miter-cut sections of 8-inch PVC pipe, cut in half, top and sides ( blind spots would be an issue ). Greyhound buses have been modified likewise.
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The DODGE military trucks which the M1715 replaced, had a slanted, split-vee screen, and the A-pillars appeared to possess ample curvature ( MASH 4077th ).
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The JEEP is 85-inches wide. As little as 3% ( about 2.5-inch radius ) of width has been shown to provide drag reduction, compared to a 90-degree transition. 7% shows 'remarkable' drag reduction ( around 6-inch radius ).
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Even with the raked screen, you'd be strongly encouraged to 'soften' the A-pillars.
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Some 'cardboard and duct tape' edges and yarn tufts would tell the tale.
