Gotta love the ’60s! The entry landing is probably part of the foundation pour and often there are ‘lights'(windows) on either side of the door which requires strong headers to support the roof.
One idea is to saw cut parallel to the wall to floor depth and jackhammer. Like a dado cut in wood. Existing structure stays intact and you build a custom tall entry door.
Guessing: $2500 cutting, 5k door, new floor?, drywall repair?…so $10k min.
