The Stovebolt Site Forums The Parking Lot Big Bolts 1957 GMC cabover

I think the model might be an F 350-8 or an FM 350-8 (8 for V8 engine)

There was also a larger 370 model, and even larger LCF (Low Cab Forward - called COE in earlier years, pre-late 1955 Blue Chip GMCs)

Spanky and others might know the difference in series letters/numbers.