Hollander has always had notations of minor work that would be needed to interchange parts, especially GM parts. If they say it won't fit, chances are it won't fit. It would likely be so different that even minor rework won't make it work.
Just my experiences because in the last 50 years I have used Hollander interchange to save my butt, and money in my profession.
58 Pontiac 2 dr sedan is probably gonna be a little tough to find, since there were far more 2 dr hdtps and convertibles made. Someone may be able to weld the upper part of the old sedan door frame to a hdtp/conv door if you have the old parts, the window, and regulator. If the old door is missing you're out of luck to even fabricate one from 2 old doors.
I really didn't think chevy, and Pontiac used the same doors, back then each division had a lot of things in their cars that were different. I know for a fact that even though chevy and Pontiac both used the X backbone frame, the frame and suspension was completely different, nothing would interchange in that department.
