I have a 1966 Ford F-250. I am trying to replace the rear passenger side wheel cylinder, but I have ran into a small snag. There are 3 flat head screws holding the drum in place. I have sprayed them with penetrant oil and have hit them numerous times with an impact screwdriver. I have now come to the point where I am willing to fire up the oxyacetylene torch and blast the screw heads off. Does any one have any experience taking these screws out in a more traditional manner. By the way the truck has no working brakes and I can not take it to a repair shop.
“ErictheCarGuy” has a YouTube video showing the ball-peen hammer method of loosening flat-head screws - it works for me about half the time. Give PT-Blaster a go at it. You could drill the heads off if you don’t want to set up the torch. Oxy-acet will blow the screw heads to kingdom come in almost zero time.
I have torches, grinders…all the best medieval implementations 
but I would probably choose to drill off the heads over using a torch…
The drum can be removed with the hub attached. Remove the axle shaft, loosen and remove the axle nuts and outer bearing and pull the hub. With the drum on a work bench it should be easier to remove the screws or leave them. It will be easier to repair the brakes with the hub off.
My experience has been with Honda drums and rotors. They also use flat head phillips type screws to hold them on. When necessary, I have always just drilled them out. It’s quick and simple. I like to use a reverse drill (the kind used for removing broken bolts) because at some point it will often back out while drilling but a regular rotation drill will work fine.