i was told by the guy that did most of the factory Z restorations that the '73's have thicker sheet metal.
Also '73's have japanese made flat top "SU" style carbs and a smog pump due to emmision regulations. I'm sure there are other differences...
The 70 and early 71 had two little grilles on the deck lid and had 240Z emblems on the rear 1/4 roofpanels. The differential was also located a few mm forward on these models. The ash tray was in front of the stick shift instead of behind it. When you remove the ash tray on 72-73 models it makes a great cup holder! The seats have a knob on 70-71 240Z for seat adjustment instead of the common lever on later models which allows you to fold the seat forward. The climate control panels are different as the later panel has lights in it. The oil preesure gauge goes to 140 psi on 70-71 instead of 90 psi The carbs on a 73 SUCK!! Differences in heads. E31 on 70-71. E88 on 72-73 and I believe the 73 has larger exhaust valves. The 73 has 9 mm rod bolts. the bumpers extend out further on 73 240Z's. The neat storage panels under the parcel shelf are not found on 70-71 Z's. The inside door panels are better quality on 73 Z's. the seat belts are better also as they retract on 72-73 models. The 70 -71 had locking gas cap doors as well.The 73 Z's were slightly heavier also. There are probably other differences but I can't think of them right now. I'll post more when my memory kicks in.LOL Later,norm
here we go. 70--1st year, different emblems on the c-pillar, different hubcaps (went to very early 71's) and e-31 heads. 71--newer c-pillar emblems, most with e-88 heads, no hand throttle (which 70's had). 72-- reclining seats, no more latch on the gas lid door, mounting points of the rear end moved back to make half-shafts perpendicular to wheels, new hubcaps (like 71&1/2-76). 73--flat top carbs w/more emissions, resulting in vapor-lock when hot (thus--hard starting), alot more emissions, rubber inserts in the bumpers between the bumpers and the body, and a whole lot of other minute differences which would take days to describe.
hope this helps,
You guys are great!
Some more differences on 70 and early 71 's are 3 piece transmission, lighter flywheel, metal radiator fan, AM only radio, console, hatch trim panel, no preheat on the air cleaner, vertical rear window defogger lines (or no defog on earliest), driveline, bumper guards, ignition switch design(and keys), metal emblems, steering wheel, and much more than I can remember on a Friday night.
Datsun added slots (holes) on the steering wheels to allow more give in an accident(early cars are solid).
They also added side impact bars in the doors, intermittent wipers, 2 position door stops so you don't ding the car next to you, better ventilation system, and changed some of the guages.
Now, I'll turn it over to the next person, as I know there are more. Joe