let me first start by saying, I'm not an expert. I learn something and love sharing it. If there's a better way please let me know. I decided to put this up cause I can't think of a better way or even another way that doesn't involve a bunch of bondo.
If you have seen these tail lights on show cars they fit perfectly but even factory ones on a factory quarter are far from perfect, VERY far from perfect.
I first started by widening the quarter top. The other side, which was factory, fits much better up top to the tail light but on the repro it was waaay to skinny. So I cut a slice at the very peak up top (and should have stretched it out further), then cut slices in the jamb because that 45 degree created by the jamb won't allow the quarter to move accurately as needed. So after I cut my slices I pulled up on the cut at the peak, held up the tail light, and then removed the tail light. With the tail light out it will show me which slice in the jamb has moved the most so I tacked that one in place. Without tacking more of them I repeated the process of pulling up on the peak, putting on the tail light, and then quickly removing and tacking another slice. Once all your slices are tacked you don't have to hold up the quarter any more, it will stay. Then you will have to create a patch to fill in the gap on your slice at the peak. I shaped mine before welding it in and was sure to cut out more metal than was needed by matching one end of the patch to the edge of the slice and then scribing onto the quarter where to cut. Making the patch bigger makes the transition smoother just as it would have been if I made that slice on the peak stretch out farther.
So once that was done I was in the ball park but the bottom area by the tail light needed to go in, so I cut a slice in the jamb and a couple going across that at the 45 to allow it bend at those points. Then I hammered it in and tacked So now it's in the ball park for MUD!!!!... kidding. Ok, now you do the rest at the tail light. You will notice that there will be gaps between the chrome bezel and the quarter. So you hold it up there and you'll notice the actual tail light housing is what's giving it the gap.
So you first take off the bezel. This is also a great time to lightly bend the bezel(without cracking it!). On mine the bezel stuck out a butt hair in one small area up top. So with the bezel off it was easy to bend it in that area. In one small area on the other side the lower part of the bezel had to go out. So I knew if I bent that area out it would also bring it out in other areas, so I had to bend that while it was on the housing, while holding tight to the area I didn't want to bend(to keep it in place) and then using a screwdriver to pry it outwards. Worked like a charm!
Next I had to take off the rubber seal cause it was too close to the area that I needed to grind down.
this is the area that you grind down to bring the bezel closer to the panel. What makes it take time is that you don't want to grind off too much and you can only check your progress with your bezel ON, and with the bezel on the chrome bezel is waay too close to the area you grind down so you have to take it apart every time you grind on it and put it together to check the progress. So you'll be doing that a couple times and it would be wise to file it smooth afterwards. It's tedious work.
The last steps are easier for sure. You then glue back on your rubber seal and then mark where the housing has to be width wise when you screw it in. This is important cause you don't want to use a step drill on a hole after the car is painted. Anyhow, I made the mistake of marking where the housing has to be AFTER I shaved everything, which made it harder cause now the bezel is right on the quarter. So next time I will mark the width before hand and am conflicted on putting a tiny scribe mark in the jamb before paint to tell me where to tighten the housing up on final assembly. makes sense and is better than scratching the paint trying to fit the tail light in there 3-4 times. Why not do it once and live with a tiny mark no one will ever see?
Once you do all this you might have a very tiny miniscule amount of filler that's needed but it won't be anything that causes less sleep.
If there's a better way please let me know but this worked like a charm and believe it or not it was suggested that I lay in fiberglass filler in the jamb, and with the tail light taped up lay it in there while the filler is wet so it instantly takes up the right shape. Yeah, I think I like my idea better.