Interesting tidbits from the 51 GMC owners manual.
When breaking in your motor you should drive under 40 for the 1st 500 miles. (they don't say anything about break-in oil, or weight of oil for break-in)
20 weight oil is recommended from 32 to 110 degrees. 30 weight is only recommended from 90 to 120 degrees. 5 weight, or 10 weight diluted 10% with kerosene is recommended for operation from 30 below to 40 above.
The 1951 manual lists only 228 and 248 motors. Under "Weight Capacities" it lists a gross combo weight for a 350-24 as 26000 lbs. (Pretty good for a 248.)
Rear axle rating for 1/2 ton is 3300, 3/4 ton is 5000, 1 ton is 7200.
5 speed trannies were optional for model 300-24 on up.
All models had a built in radiator overflow tank within the radiator top tank. Only Cab-overs had a pressure type radiator. (It apparently used a sealed cap and had a pressure release valve.) All other models had an "atmospheric" type radiator. (I'm not sure what this means. Does this mean it had a sealed cap, but had a non-valved overflow tube?)
Windshield wiper washers were an option, as were wiper vacuum boosters.
