I have compiled a list (from my memory) - anyone else have any more? - there was a good thread about a year ago outlining some of the differences, but I guess it is gone now - not in my favs or search for???

A few things I have found

1. Grills are different between all years, 67-68 will swap though
2. Header panels are different all three years, again 67-8 will swap, 67 has PLYMOUTH spelled out, but '68 had it as one word, '69 had a bump in the center, '67-8 were flat along the top.
3. 67 has a one year only idler arm
4. 67 was the last year for the 273, the 68 got the 318/340/383 (the 383 was avail in '67)
5. The wiper motors are different
6. The fish emblem is bigger on a '67 and placed at the front of the fender, 68 is toward the back
7. '67 has no side markers
8. '68 grill/fenders has another hole in the left and right ends of the grill
9. '67 used the inland shifter; sometime in '68 they moved to HURST
10. in a four speed, the output shaft yoke is the small dia (the 904 style) the later ones used the large 727 yoke
11. The '67 used a smaller (3 speed) output bearing on the 4-speed then the '68+ (it was the same for '66 BTW).
12. The 67 used a smaller 9.5" clutch and the later ones used the larger 10.5" - the belhousing on a '67 is cast iron as well, and later ones are Aluminum.
13. The dash is different, the pad only covers the top, '68 the pad has a "knee pad", and 69 only covers the top, but the top pad is different.
14. The dash bezels are different - the '67 had the cig lighter in the ash tray
15. The glove box door is different as well; both in the hinges and the handle; '68's have a button (I think??)
16. The glove box cardboard box is different - it attached differently then '68+
17. The tach for a '67 is different then a '68 the sweep range is different
18. '67 the trip odo was standard, optional in '68+
18a. The speedo cable was different - it screwed into the back of the speedo in '67 and snapped in in '68+
19. For a 'vert, the inside around the window trim is painted black in '68+ in '67 the a-pilar moldings were plastic chrome and the upper part was chrome.
20. The wing ding (vent window on the door) channel and handle is different between the years, '67 has a straight handle, 68+ curves in torawd the door.
21. The doors are different, '67 has a screw holding on the wing ding (vent window) which can be seen inside the car, '68 had a plug there, '69 had nothing,
22. 67 + 68 have the door vents in the front of the door and the bottom (behind the front seat), '69 does not
23. The side view mirror was moved in '68
24. The door lock was moved in '69 up torward the driver
25. The door panels are different
26. The seat frames are different, '67 used the '66 style with steal trim for the back and bottom, '68 used something different.
27. The console was changed in '69 to a wood grain insert, the '66-68 had a black strip - both 4 speed and auto
29. The arm rests are different on a '67, they have something like a "shelf" that the pad mounts to, 68+ used the later style, which were used until '76
30. The door hardware is different, the window crank on a '67 is all metal, '68+ used a metal bar w/plastic handle
31. The rear door panels are different, but the converts are the same.
32. The gas cap is different in '69 it said "FUEL"
33. The gas tank is differen in '67 - it used one strap going from left to right, 68+ used two straps going front to back.
34. '67 had single exhaust (I think the 383 had dual, but not sure) 68 had dual exhaust.
35. '67 did not use chrome exhaust tips - the hi po cars used the 273 resonator system
36. The reverse lights are different, '67 used the long style (I think) '68 had none (they were in the tail light) and '69 used a shorter style and a longer style, but I think they are different then the ones used in '67.
37. The trunk lids are different, they have different emblem holes.
38. '67 trunk trim was 3-pieces, '68 was two, '69 was one
39. The tail lights are different for all 3 years
40. The vin number on a '67 is on the a pillar in front of the door, in '68 it is on the dash
41. The dash frames are different (the glovebox lid + plastic dash + the '68 is purforated along the top under the pad - '67 is solid).
42. The radios were different, '67 had knobs, '68 used thump wheel.
43. The '67 had the horn relay under the hood (near the horns) and in '68 it was moved under the dash
44. All 3 years used different rocker panel moldings, the '67 were thin (about 2-3"), '68 had a thin spear, with a pot metal piece with fins near the rear wheel.
45. The optional wood grain on the upper dash bezel was different on '69s compared to the '67-'68 style wood grain
46. The window lock strip was different in '67 vs. 68+ (for both the front and back windows), in '67 it used a lock strip (like the '66 and the 80's trucks) and in '68+ it was glued in and had stainless steel trim. - The vert used the same style for all 3 years though (lock strip in the bottom & stainless trip around the top)
47. The convt top & vinyl top were different grains in '67 & '68 (and maybe '69).
48. The hood trim was different for all 3 years, '
'67 used the thin fins for all models, '68 used callouts on the HP models, and a simpler design for the low po models,
49. The hood was different '67-8 to '69.

That is all I can think of off the top of my head...

6t6