And, like Ah-nee, I'm back.
So this is what the passenger side inner door shell of an 85 Monte Carlo SS looks like. The detail shot is the tape measurement of the physical width of the door, 58 inches or 2 inches shy of 5 feet.
The first picture in this sequence is a detail shot of the hinges, in this case, the top one which also carries the detent spring that works with the lever to hold the door in situ when open.
Because your door is both still intact and still hung on the A pillar, this is what you will be looking at if/when your need to adjust the door forces you to deal with the hinges. As you can see the bolt heads are semi buried behind the structure of the hinge. They can be got at using a 3/8ths power/johnson/breaker bar and a 6 pt 11mm shallow socket for the initial tug and then an 11mm gearwrench or similar. They will not only be tight but possibly rusted or glued in place by seam sealer if still factory undisturbed.
You mentioned the possibility that tweaking or slightly shifting the position of the latch striker pin might be your solution. In the first of these shots you can clearly see the shim that was placed in behind the striker pin. Adding shims like this has the effect of moving the pin away from the door jamb which puts it deeper into the latch mechanism. You might get away with one more shim but after that the head on the pin would likely crash into the back wall of the latch. i did mention fender washers as a basis for making a shim for this pin.
The second picture here is just of the T-50 torx socket that you will need to deal with the latch pin. Be sure that the torx head is buried square and completely into the pocket on the pin head or it can twist out, which can tear the "teeth" in the pin and lead to complications.
Remember when I mentioned that my inner door shell might be twisted? Well, judging from the apparent taper, the shell definitely isn't sitting square with respect to its location. Referencing back to the picture of all those hinge bolts, it would be the three upper hinge to door shell bolts noted in the one shot that would have to be slightly loosened and then the door pulled straight out to get the upper half of the door to move out or away from the door frame. As I also pointed out, the pivot point for the rotation that needs to be applied to this door would be at the lower hinge. In this case, of the three mounting bolts, it would be the pair of two that would be the loosest and the single bolt off to the side would be only loose enough to allow the door to move.
If the door was flush and lined up flat with with quarter panel but the door line did not match, then it would be the hinge to A pillar bolts that would be slightly loosened to allow you to pull straight up on the door to raise the latch end higher. Again, I have to point out that you are dealing with more than one dimension when you go to adjust a door. You may think that a quick pull on the door will lift it the amount you need, only to discover that while you got your lift, the door now sits either proud or sunken in its door frame. Truing a door is a walk away exercise: if you get frustrated, Walk Away, otherwise make sure that the wrench you end up throwing in frustration is a Harbor Freight Chinese cheapie and the direction you throw it in has nothing of value for it to hit and damage; people included.
For my own project, this is the replacement inner door skin or shell as I call it. These shots should give you some idea of the physical size of this part and the tale of the tape I posted above explains it all. What you are not seeing under its masking paper cover is the door side. it is not much different than the one in the first shot except it is a lot cleaner and has a fresh coat of grey interior rust preventative. Rust can germinate as much from moisture trapped inside the shell as it can from salt and crud eating away at the outside.
Finally, allow me to introduce you to one of the most dangerous components in a Monte Carlo. Physically it doesn't look like much but for the potential to maim and injure it is right up there with one of the front suspension coil springs!
This is the power window actuator. This one is upside down so what you see is the mounting flange and the motor drive. At the top, and mostly visible is the sector gear. if you were to flip this over you would see the reduction housing that holds both the drive gear and a viciously nasty preloaded coil spring. It is that spring that will cause the damage if, for whatever reason, the reduction housing breaks or gets damaged. Do NOT try to separate the motor from the drive section, that is guaranteed to hurt. If you have to deal with this unit, use a pair of vice grips to clamp the sector arm to the mounting frame so that even if things go horribly bad, the arm is pinned and frozen in place. Left free to move, you are dealing with the equivalent of a pair of king-sized scissors; and the damage they can inflict is about on a par with their size. How do I know? Ask me sometime.
So anyway, just a bit of what fits what for you to check out. Hope it helps.
Nick