The Spirit of America Three Wheeler runs on 8.00-39 with a 48'' outside diameter.
The Spirit of America Sonic (1965) used 8.00-25 with an 36'' outside diameter on the front and 8.00-39 on rear.
The Wingfoot Express II (1965) used 8.00-35
The wheels looks very close to the wheels the Express II shows on the car during the building periode in Walt Arfons workshop.
So the possibility "Express II" with the Jato rocket could be right.