fred my suggestion is first loosen the seized bolts then try the method described in the manual , i can assure that it does work as long as you can do all the steps the manual describes, i would try an impact wrench on the seized screws and leave the body jack as a last option

The hinges are held to the door with cap screws. You need to loosen these screws to make the adjustment you require.

To get access to the cap screws you first have to remove the door panel.

It helps to loosen the screws, move the door around until it moves freely, then snug up the screws so the door will just move.

For loosening frozen door hinge screws (the ones that hold the hinge to the body) you can buy a big Philips bit that goes on a 3/8 drive socket wrench extension.

Heat the screw with a torch. Set the screwdriver in the screw. Tap it with a hammer. Put on the ratchet handle, and it will unscrew. Push the screwdriver in hard so it can't slip while you do this.

It helps to remove or disable the latch when doing a door adjustment. You want to be able to close the door completely without the latch, so you can check your adjustment.

Adjust the door until it is centered in the hole first. Then adjust in or out so the door is flush with the body at the back. Finally you may have to adjust the fender to the door.

In most cases of a car this old, the rubber mounts under the rad support have squashed away to nothing, resulting in a front end sag. This makes the door gap too narrow at the bottom. You have to replace the rubbers to get the fender to fit properly, or at least shim up the mounts with washers.