Your Toyota is not unlike Kamm's K-form cars of the late 30s,early 40s.
His personal car,pictured below had Cd 0.23.If you mimic'd these mods (including the full belly pan) you'd have a shot at the same drag coefficient.
A receiver-hitch-mounted boat tail would help with the length necessary.
For lower drag you could keep elongating,as with the Mercedes-Benz C-III,with Cd 0.178
Here's VW's 1981 full-tail 'Flow' body,Cd 0.14
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As others have mentioned already:
*clean up the nose,get all the air over and around,not under,minimize your cooling air to 'just enough'
*do a complete belly pan
*clean up the sides,dropping the rocker panels down even with the pan
*'basjoos' your wheel wells with articulated spats up front,simple skirts at rear
*add as much boat-tailing as you can tolerate (this is where all the money is)