I didn't replace my roof on my 1948, but I did fix the dents the and oil canning. I didn't have any experience heat shrinking, but took my time, watched a lot of videos and got the oil can out and only had to use a little body filler to fix dings I put into it. I would give it a try, since you are thinking about replacing anyhow. The good thing is you can reach the other side with a dolly, if you have the rear window removed. What have you got to lose?
Now, the rear panel on my truck was badly dented, which I didn't know until I went to remove the old paint for a re-paint. I found what must have been a large tin of bondo used back there. The difficult thing is, you can't get to the interior side of the rear panel because of the double wall. I tried using a stud puller, heat shrinking and even cutting pieces out and replacing, but I was making it worse. So I did get a patch panel for that. It was easy to install, and fit great. It was fun learning what my limits were. I think putting on a roof patch panel would be pretty critical in fitting because of the front windows. Maybe someone will chime in who has done it.
