Re: How to install old slab 1 3/4' doors
Your major problem is that modern interior jambs are set up with a 1-3/8" door stop (trim in the center of the jamb ). While you can probably "make" the thicker doors work, they're not going to look right unless you move the door stop trim forward in the openings to accommodate the extra 3/8" thick doors.
If the doors you're installing are solid core, then you will have to install a third hinge, as again, most modern interior doors only have two and you will need the extra hinge to help out with the added weight of a solid core door.
If you want to move the stop trim, then run a knife down either side of it to cut through the paint, then carefully get under the trim with a small pry bar and work it loose. Another option would be to take the new doors to a door shop and have them fabricate new jambs and hang the doors for you, then you would remove your existing doors and install the new jamb/door combo.
Whatever you decide to do, changing the doors is going to be a major effort, for a variety of reason.
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