Chevy & GMC Vans

I have saved all info available on adjusting the slider on Gen II. Finally tried it yesterday and.... I hate Gen II ! I have done searches and need to ask.
I removed and slotted the black plastic part that inserts into the jamb hole. This did bring in the front of the door. On the rear of the slider, what exactly adjusts the door in? Moving the hinge plate on the edge of the door or the double post on the jamb??
And my experience with how dumb GM was in building this, I am afraid to remove the post on the frame for the front door. WHY??? Cause the idiots ,I am afraid, let no provision for holding the nut in place and if I remove the post, the nut will fall down in. Can I remove the post? I need to slot it so I can make a small adjustment to the front door.

My side door has been out of adjustment for a while. In trying to get it tight when closed and aligned, I am seeing that when this conversion van was repainted, the doors were not perfectly aligned. So now, when I shoot for perfection, I have to note how the stripes line up instead.
So, how do I adjust the rear edge of the slider in? Can I remove the front door post without losing the nut inside the frame?
Thanks.

You should be able to loosen adjust the rear striker in/out up/down. As far as the front post, I assume you are talking about the front striker? Not sure why you would want to remove it, you can just loosen it and adjust.

The front post striker is screwed into a square block that is about 2"X 2". All the adjustments I see in my FSM are loosen and adjust.

Thank you. The strikers post I mean, is on the front door. mine is a '98 and there are only round holes on this and the other "adjustable" items. So I need to remove the post to oblong the hole to be able to make adjustments.

Reports are conflicting on whether the block will drop or not. Some have had success, some have had to open the trim to retrieve the block.

If you have a bad ass magnet, use it to keep the block in place.

I have replaced these post on several vehicles including GM and have not had one fall but I just may be lucky.