What I remember (I've had a 67, 68 & 69 years ago) on 67 vs 68 appearance:
Grilles, header panel letters/nameplate
Hood ornamentation
Fender nameplate & location
Windshield seal & moldings
Back glass seal & moldings
Tail lamps, trunk panel
Backup lamps moved into tail lamps & side markers added.

I don't recall the dashes being much different except for 68 had a lower pad added
Interior trim changed yearly.
Not hard to pull off, but a bit spendy...