That's a 450 series 3 ton you have there. The "45" in 452 denotes a 450 series, the "2" in 452 denotes a 149in. wheelbase. The "30" denotes it has a 302ci. engine in it. 9379 is the production number.

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