I got to work on my cab on my 1964 C-10 fleetside yesterday and ended up cutting the entire top skin off of the roof. Someone had bondoed it and once I started poking I ended up with quite a few holes.
It`s mostly just along the drip edge and about 1 inch up into the top skin. I hate to go the cheap route and fiberglass it or similar. Since I have the top skin off I would be able to cut out and treat both sides really well. On the other hand I don`t have a mig welder and even a cheap one at Northern Tool will cost me 250.00 or so. I have some other stuff to patch up too, so I would probably use the welder. The other way to go is a guy here locally has a 1964-66 big window cab he`s selling for 400.00, but I probably wouldn`t be able to tell if it has hidden rust damage, even though he states it has minimal rust. I guess my question is, do you guys think it`s more to my advantage to try to patch the cab myself, and in the process learn more than I now know about metalworking or is it just too much trouble to do work on the drip rail area.
Thanks, Mike  

First if you are going to keep monkying with old cars,trucks you should buy a welder and don't get a cheep one get a Lincoln or Miller with argonCO2 gas. You don't need a big one just 110 volt it will weld up to 3/16 thick metal. You also need a lot of practice before you can start welding on your truck.Ron Covell (professer Hammer in the back of the classic trucks) has some vidioes you could get to help its not hard you just need to know how before you start.
You are not going to find any patch pannals for your roof you would have to find another to use or some pannels with the same curves to use. So the big window cab sounds like your best bet. You can take a magnet and run across the metal and it will stick less if there is bondo. Besides the big window were a option and there not that manny out there so it would be worth it.
If your roof is bad how about the rest of the cab,door bottoms and such? Check the floor under the mats. I have a truck that came from Oklahoma and thats was the first thing I tore out found one hole under there. I have a big back window cab 65 with the floor rusted out back of the gas tank were it meets the back otherwise good. You could have for little or nothing but I live in MN. So that wont do you much good.  

I`m kinda looking at fixing mine because it is a big window also, and like I said with the roof skin off I can treat both sides and a little ways at least down into the pillars etc. The pillars and the front,rear and rockers seem to be pretty solid. The floor has no carpet or mat and I can see a couple of patches next to the doors, so someone has patched it before. With the patches the floor as well seems pretty solid. I`m not really concerned about filling in the section between the top roof skin and the drip rail, but the drip rail itself has a couple of places that are eaten away, so I will have to form another section of rail. What is the sealent you use in the bottom of the drip rail that seals the outer lip of the rail to where the roof panel joins?  

Just use seam sealer