Tiny,
My guess of 300 units is a little (bad) joke.
Here would be a better guesstimate:
In 1950, 6.55% of all Chevrolet trucks were 1/2 ton panels.
The guess (above) was no more than 75,000 1955-1st production.
That would make 1/2 panel production to be about 5,000 units.
Useless information - top ten models in 1950 (rounded up)
Total Production = 422,832 Chevrolet trucks
1. 3104 = 42.5% (1/2 ton pickup)
2. 3604 = 12.7% (3/4 ton pickup)
3. 6403 = 10.0% (2 ton chassis and cab, 161" wheelbase)
4. 3105 = 6.6% (1/2 ton panel)
5. 6103 = 3.6% (2 ton chassis and cab, 137" wheelbase)
6. 31x6 = 3.5% (Carryall suburban - total of end-gate and rear doors)
7. 4403 = 3.4% (1.5 ton chassis and cab, 137" wheelbase)
8. 3804 = 2.0% (1 ton pickup, 137" wheelbase)
9. 3803 = 1.8% (1 ton chassis and cab, 137" wheelbase
10. 3805 = 1.6% (1 ton panel, 137" wheelbase)