Assuming you are either body-kitting the car or just replacing a dented section (in other words, not looking for Concours level work which would require the spot-weld fun noted by the others)...
Air chisel is the absolute best. I bought one after a friend loaned me his - it takes the fenders off like butter and doesn't leave a jagged, rough edge like a saws-all will. I had used a saws-all in the past, and when doing the Sheridan kit on my car, that is when I discovered the chisel.
I just drew a cutting line with a black permanent marker like I did for the saws-all, and followed along with the chisel. Maybe one minute per fender (no joke, that fast once you're cutting). For complex angled areas like near the valences, you can finish with a cut-off wheel or saws-all and just have that area to fix the jagged edges.
The donor car can air chisel a bit larger and fit as needed. That is your "standard" body work kinda deal. Again, if you are an "absolutely no filler" kinda guy, then get the drill and have the patience of a monk
