Click on the 1947 link to see the whole profile of the Saab Model 92:
Saab History - Saab Parts USA
Also, although not an aerodynamic feature, models 92 through 97 had free-wheeling clutches which could be locked-out when necessary via a T-handle near the gas pedal, and the the 95 and 96 models (and likely all earlier ones) had full underpans made of metal. The engine bay was fully enclosed, with vents inside the front wheel wells. I was hypermiling my V-4 4-stroke 95 in the early '70s, but the mileage although great at the time isn't so good by today's standards. With careful gallons vs. distance measurements I was getting 36 MPG as 50-55 MPH, with a straight line decline to about 22 MPG at a steady 75 MPH. These were measured repeatedly on long stretches of I-80 in Wyoming, repeatable over several years.
Also, I had an analog MPG meter, with speedometer cable insert and a flow meter in the fuel line. I eventually burned it out after pegging it many times while freewheeling on the interstate.