Per, this is a tough call.
1.) your core support and drivers side inner framerail/splashshiel have definitely taken a good hit. It may be relatively local to that area, but it is unlikely. Many times the framerail kinks just forward of the firewall on the side of the framerail that faces the engine/exhaust. I have seen this first hand, so there is a good way to check before you dismantle the car.
A.)Get the car up in the air, high enough to get under it. If your engine is removed it's easy, but if it's not, follow these simple directions.
B.) look at the inside surfaces of the framerails, and compare them closely, with your hands, eyes, and pictures if you can. If there are no differences, then consider yourself lucky.
C.) if you do find discepancies, mark them with a wax pencil/ oil crayon.
D.) with your body manual(service manual/shop manual, etc)
chart/record your measurements on the front end alone.
E.) compare the measurements. If the measurements are off 1/2" (15mm) or more, it is time to visit the frame shop
2.) cars built in the 60s/70s had HUGE tolerances,(1/8" to 1/2")
mainly because cars were assembled by humaans and manual fixtures. Gap quality
did not become prevalant to the mid-late 80s. Most of the time, panel fit was nominal, meaning the gaps were closer to the 1/2" side.
3.) many parts will display a misbuild because the panels built 1/4" here, 1/2" there, leaving huge gaps. Not to worry, it was pretty standard.
As Burdar said, his car is being gapped, which is a very common practice in high dollar/quality restorations. The process omits the nominal gap situation caused by manually fixtured parts from 30 years ago.
So, in summary, check your car first with some close up visuals.
If you do need to remove anything, remove the panels from the front.
Double check your measurements.
Order new parts where necessary.
Remove old parts.
Mark/record where your door hinges are, in case you need to do any door removal or adjustments.
Straighten the frame if needed.
Hang new parts.
Assemble/gap.
Perform body prep with doors and wings on, fully adjusted.
Open a beer and celebrate. You have successfully and correctly fixed a timeless car that will certainly be around a lot longer.
Dan