I've measured the bars, from big trucks, & pickups, & I'm coming up with the same measurements. I've probably disassembled 15-20 grilles, in the last 20 years. Only difference is the back bars, & grille frame.

Spanky Hardy
Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers

1948 Chevrolet 5700 COE Holmes HD W35 Wrecker
In the Stovebolt Gallery
More pictures on Photobucket

1950 GMC 250 1-Ton
In the Stovebolt Gallery