As mentioned in another post regarding chassis paints, your truck,assuming it's the '47, has lasted 63 years so far.
That was with fairly basic protection.
So what ever you do,it'll be an improvement over the original.
I agree with Alvin though,it's pretty much what I did with mine.
You can buy radiator paint brushes for those 'hard to reach' places.
It's going to be a long time before I need to worry 'bout it!