If the screws serve the same purpose as on the 3/4 tons (I think they do) they hold the drums to the hub assembly and need to come out to remove the hubs from the drums but not to remove the drum/hub assembly from the axle. It takes a lot of perseverance to get them out and a really big screwdriver
Seriously though, soak them in penetrating oil for a day and make sure you are using the right size screwdriver, even a slightly smaller one will just tear up the head (experience talking here). When all is said and done, the screws can be replaced at your local hardware store. Just bring in one of the old ones and match up the thread size. They will not be exactly the same, but they fit well.
