Tan softopper on gold dc?

Someone else I'm friendly with here did theirs with a grinder. I assume w/ cutoff.

 

I used method, but in the future I'm going to use a longer (like, maybe 32") scrap piece of 4" plate, because of the shape of the bedside you're unable to drop the tape straight down to your marking point, which I think makes your line a little wonky. Otherwise mask it off where you think you'll be cutting, mark pencil lines every 3" or so, then if you can find a good, flexible straight edge (doesn't make sense...), connect all the marks. The corner is the hardest, so maybe mark lines closer and fill them in free hand.

Then mark it off with sharpie for a clear and easy guide when you get to cutting. As far as what I used to cut, I don't like using sawzalls, they're too violent, so I used a 4.5" angle with a fresh wheel, it sort of melted through the fender, but did fine. The corner and behind the fender were the hardest - there's an absurd substructure beneath the tail light (make sure you've got the wiring harness moved out of the way), a long sawzall blade would be useful there to get in deep, but I didn't have one handy, so I had to use a dremel and slowly trim it away.

Otherwise hit it with some paint, throw door trim on it, and you're set. If you're still concerned with rust, you can run a super thin bead of RTV inside the door trim before you put it on and call it good. I might do that eventually myself, but the door trim fits really really tight, so it might just be a moot point.