Michael,
How these cars were ever moved along an assembly line at any reasonable speed is beyond my comprehension. If you look at C1 Corvette windshield/door post lineup you will see all types of misalignment. It is true that some of this can be adjusted out but some can't.
The '59 I'm almost done restoring is a prime example. I had to modify body shapes to get reasonable fit. The post on the passenger side was a prime example although I'm sure there was some body damage in that area, I had to find a door which fit better and modify it so it all lined up. The gap left is acceptable but not perfect. The driver side came out very good. Now I'm putting side glass in and the moment of truth will come when I attempt to line the windows up to the hardtop. Hoping that will go well.
I don't have any special tips I can give you on the posts. The windshield is a fixed location and if it's got glass in it and it's mounted I assume it's correct. Play with the post with shims to angle it how you want it or even enlarge some of the mounting holes if you need to move it more. I spent a lot of hours doing these.
Attached are a before picture, another showing buildup of the fender with glass cloth. I don't have a shot of the post right now but here's a picture of the almost finished car (you can see a slight gap at the bottom but the top and weatherstrip fits very well - been in the owners garage 34 years and I've put 4 years into the restoration. This shot is the owner taking it for a spin to get it registered.
By the way, the posts were so difficult to get aligned, I painted the door tops where they go, then mounted them before painting the car.
Gerry