1940-1946 had a rectangular instrument cluster.

GMC would be seen on the speedometer if it was a gmc. Another indication of a GMC is the oil gauge. GMCs had a 60 to 80 lb gauge. Chevy had a 30 lb gauge.

The yellow truck has a 216 (Chevrolet) motor in it. The other truck appears to have a later 250 in it.

John