So that reminded me that quite some time ago I was asked about the process of taking the bow out of body panels and here was my answer.
It might surprise you how much improvement you can make to the looks of your car just by getting all the panels lined up properly and gaps adjusted right. When I walk through a field of show cars that is the most overlooked thing that I see, and some of it is just minor adjustments. The odd thing is that most of the owners don't seem to even realize the adjustment problems their cars have, but when they see one adjusted correctly, they do see a difference, and consider the car a higher quality even though adjustment may be the only difference in the cars.
These adjustments should be made before paint so you can make what ever little tweaking you have to do. So I would suggest you give that a try and see how it looks before getting radical. After you make your adjustments and tweaking, you could even spray some cheap gloss paint on to see how it looks, get some pictures of it to study, and then use reducer to wipe it off.
Actually, proper adjustment is the first step in making a car straight. The OP of that question may not even be on the forum anymore, but this might be helpful for some that are on here now, and I didn't have examples back then.
Cars in the southwestern states get a lot of sun so the paint dies rather quickly, thusly there are a lot of cheap paint jobs in that part of the country. This 57 being from LA Ca. had one of those paint jobs just before I bought it over 30 years ago. Its been in storage ever since, but I pulled it out a few years ago to get it ready to sell, including adjusting all the panels. You will notice in this picture that the bottom of the fender kicks out, instead of pointing straight ahead. To fix that it requires the spot welds that hold the fender to the brace to be drilled out to allow the fender to straighten out.
If you look around at mustangs, whether its a show car or not, you might think they just have too many body lines to get everything lined up. But keep in mind these old cars have a lot of adjustments, and in some cases two ways to make the same move. Getting good panel alignment is difficult, slow, and agravating, and that can be true of the whole restoration process, so I guess it just depends on how bad you want it. But when you do get everything in alignment, make sure you drill and pin the door hinges so you don't lose everything if you pull the doors off.