I used to like the later ones, now i am tending to the early ones(I did just get two more, a 69 and a 71)
I like the vent windows, and cool shield style steering wheel pad of the early ones. I would say rust is a big issue with any vintage. Seems to be thicker sheetmetal on earlier ones.
-Discs 9/'75 and newer
-Early-7/'70 heater duct does not have the indent for the A/C unit that was an option for 7/'70-9/'73.
-wiring harness prior to 1976 ran down DS of body, later went to pass. side.
-Center Dash panel changed 3 times, early-9/'72?, 9/'72?-9/73? and 9/'73-end? Might be a end change in 79??
-Early dash has key on left until 9-72 IIRC
-Heater changed in 9/'73
-Nippondenso A/C option 7/'70-9/'73 is stand alone unit, with its own fan. Mounts unde glovebox.
-Later ND A/C unit replace heater duct and the center heater louvre was different as well.
-Early back seats bottoms had no latch.
-Pre 72? tailgates had lic.light below plate, later got the piar of lights on either side.
-P/S option 1979
-Doors went to rounded front top corner in 9/'77 IIRC. Same time tailgate lost the embossed TOYOTA section.
-Gas door lock 1975
-Keys changed sometime 76? to only one key for all locks, unlike 9/'72-76ish where ign key was different
-Chrome trim showed up on drip rails, quarter windows and windshield much more frequently in 75, not sure if it was even an option before that, but I have not seen it prior to 1975.
-Hood change for 2f aircleaner, 1975
-4 speed in 9/'73. My 9/'73 had a three speed in it, but the factory installed a 4 speed skid where none of the drain holes lined up until I installed a 4speed. apparently the 4 speed skid made it to the assembly line before the tranny did.