[aerohead]

So on the 24th,Elon Musk announced Cd 0.30 for Cybertruck,and narrowing to 82-inches.No mention about mirrors.
If you could get a long-bed,standard cab RAM,then, a Brett Herndon' Aerolid,Herndon' aerobox,plus deformable gap-seal,between cab and bed/shell would be all that was needed in order to match the drag of Cybertruck.
With a 6-1/2-foot bed,you'd need a 42-inch aerobox (boat-tail).It would actually drop you to Cd 0.299.from Cd 0.382.
With a belly pan,diffuser,passenger car mirrors,and wheel fairings you'd be looking at Cd 0.1776.And you'd be stuck there unless you went to BEV,and lost the cooling system (Cd 0.1526).23.12 mpg vs 17.0 mpg at 70-mph,on REGULAR Unleaded.30 mpg @ 70 mph with turbo-diesel (same power).
AeroStealth had a 'Cybertruck' back in 2014.He'd purchased an Aerolid and box from Brett.It dropped his F-150,from Cd 0.402,to Cd 0.305,according to CFD and wind tunnel conformation at an undisclosed wind tunnel.We ran some numbers between Monahans,Texas and Odessa,Texas,looking at 24.92 mpg,with the 3.5-l EcoBoost.Which would be around 21.66 mpg for the 5.8-L, V-8,and 28.17 mpg for a turbo-diesel,all at 100-km/h.
The rumor-mill has Cybertruck at around 68-mpg at this velocity.The motor has a really sweet BSFC-e.