I've had a few issues with poor fitting & closing original doors on my '72 K5,mostly due to the floors and rockers being replaced without me properly bracing things before I cut away the rotted metal and welded in the repair panels--when I was done,the drivers door was hitting the rear jamb before even coming close to the striker..like an inch away!.

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I also had replaced the hinge pins & bushings on the drivers side door,the passenger door was still tight,and didn't give any grief with the closing,I guess that side didn't sag or move..
I also had to put a cab mount on the drivers side,and had to jack up on the floor to get it in,that probably tweaked that side more..
..the lower bushings on the drivers side hinge were shot,no brass at all left-and the hinge holes had some wear,but the new bushings corrected that ok.
I fiddled around with all the hinge adjustments and got it so it would close,but was still hitting the rear jamb hard,and you had to pick up on the rear of the door to align the striker bolt...even with the hinge adjusted all the way forward..in desperation I ended up putting a few 3/16" thick body shims between the hinge and the door on the bottom hinge,that lifted the rear of the door up more and helped the most..still far from good though,and shimming the striker post only made it worse--but at least the door closed now--and I could drive it..
I lived with it being tough to close,rattling and knocking against the door jamb for a few months--one day I delivered some paint to a body shop on my way home from work,and asked the owner how much he'd charge to align the door right...
He went out,looked at the truck--goes back in the shop,and comes out with an 8 foot 2x4,he put some rags around it where it touched the door and floor,and heaved upwards on it a few times..the door closed nicely after that,like brand new..he said "I have to do that on EVERY GM truck that we put Tiwan doors on!"....he wouldn't even accept a coffee for payment...
The next day I sneaked a whole bundle of paint stirrer paddles and strainers in with his paint order,my boss was a stingy bastid and would give like 2 of them for each gallon of paint...all the body shops hated that!...they would always say "and give me some strainers and sticks with the paint ya cheap bastids!"...
I never understood why he was unwilling to give away 10 bucks worth of them a month,when it would have kept them happy,and increased our sales...many shops bought their paint elsewhere just because that pissed them off !...the fact we sold Dupont and was the only store within a 30 mile radius that did,was what kept the doors open for the most part...