I think the 744 was certified as a new type
If in doubt, check it out :
The
FAA 747 TCDS Nr. A20WE clearly shows, that all 747 variants are one type design, and the 747-8 most probably also will be.
Check page 15 and 16 for the new paragraphs, special conditions and excemptions introduced for the 747-400.
747-400 (continued):
Certification Basis:
Part 25 of the FAR, effective February 1, 1965, as amended by Amendments 25-1 through 25-59
with the following exceptions:
SECTION NO. TITLE THRU AMDT.25-
25.107 Takeoff speeds 41
25.109 Accelerate-stop distance 41
25.149 Minimum control speed 41
25.251 Vibration and buffeting 22
25.305 Strength and deformation 22
25.331 General 45
25.351 Yawing conditions 45
25.365 Pressurized cabin loads 53
25.571
Damage-tolerance and fatigue
evaluation of structure 9
25.607 Fasteners 22
25.631 Bird Strike damage (NA)**
25.657 Hinges 22
25.675 Stops 37
25.683 Operation tests 22
25.772 Pilot compartment doors 46
25.773(b)(2)(ii) Pilot Compartment View 72
25.783 Doors 53
25.785
Seats, berths, safety belts, harnesses 50
25.787 Stowage Compartments 31
25.789
Retention of items of mass in passenger
and crew compartments 45
25.809
Emergency exit arrangement 45
25.812
Emergency lighting 31
25.832 Cabin ozone concentration (NA)**
25.858 Cargo compartment fire detections systems (NA)**
25.1103 Induction system ducts and air duct systems 45
25.1401 Anticollision light system 26
25.1438 Pressurization and pneumatic systems (NA)**
25.1529 Instructions for continued airworthiness (NA)**
etc.
So the 747 essentially
is a 1960s design meeting 1960s safety standards.