I admit that I'm rather confused, as all the 320s had the enlarged wings and increased tank capacity (over prior models), but it seems that until the 320B introduced different engines (JT3D-3B) as well as a stretched fuselage, and the "Advanced" introduced leading-edge flaps, the range was still under 4000NM
Yes, you are confused.
The early Intercontinental 707-320 and -436 models had the same fuselage length, but a different fuel tank capacity.
-436, yes normally operated non-stop LHR-LAX....just (as I have described previously).
In addition, AirFrance operated their 707-328's non-stop to SFO as well, from ORY....just.
Likewise, ORY-LAX...just, using JT4A-17 engines.
I remember these flights well, as they would request a direct routing LAX, as they were a tad short on fuel.
PS:
All of these early -320/436 (etc) models had partial LED's (leading edge devices)...
except, those aircraft originally delivered to South African...these had full span LED's.
Gotta know your airplane....and yes, later on, I flew 'em all, after they were later sold to 'new' operators.
NB.
'Advanced' referred to the cowl design.
Original...(on fan engined airplanes)...old cowl (small inlet doors).
Advanced cowl...large inlet doors.
Made a big difference to takeoff performance.
Big time.