In attempt to figure this one out;
The shape has a lot in common with the Thunderbolts Temulis worked on with Chrysler?
The cab seems to be very close and deep >>going forward.
Perhaps a front cargo area, engine in the rear.
This somewhat leads me to think of Tuckers.
The fold away headlights lead me over to Gordon and Bens work, initiating in 1933-34 pop up headlights>>respectfully.
I believe that Flajole?sp, also designed and rendered a few drawings like this also.
Since you discarded the early 50's, is it late 50's
Are we getting any closer Carnut
?