[overlap]

Welcome,
Looking at the pictures you provided the door glass or quarter glass is out of adjustment or there's a problem with the regulator, track, and etc. internally. Looking at the door gap at the rocker panel and where the door meets the quarter panel, it's not any different from most GM cars of this era.
This isn't to say don't do any frame or suspension mods, I say go for it with some discipline and planning and you'll have a nice ride to enjoy.
Gerald