What is your goal....Are you just curious about what's not original? Do you want to take the car back to original? If so, how far? Your end goal will determine the direction of the path you take and how far down that path you go.
There are a lot of different kind of values, and each of them varies. The following are different....insurance, estate planning, fair market value.
Things that stick out to me on your car as not being original....
-In-line fuel filter off the gas tank
-Your photos show two different sets of door panels, diamond stitch set incorrect
-Your photos also show two different center consoles, black/dark center console incorrect
-Speakers in rear parcel shelf are aftermarket, and carpet has been cut up
-Seats have been recovered, headrests not done properly. Seat bottoms appear to have too much padding
-Someone added replacement stickers under the hood, odd and incorrect placement
-Half of the brake booster vacuum hose has been replaced with the wrong material. 2 halves are non-matching
-Convertible top storage compartment should not be carpeted, that has been added
-Convertible boot lid re-covered incorrectly- Multiple pieces with contrasting stitching.
-Hardtop headliner and wood appear to have been dyed black
-Dash wood has incorrect finish, too glossy
-Visors have been replaced, shouldn't be black
-Dash has been recovered, incorrect stitching
-Original window sticker says "U.S. Equipment", but has KM speedo
I hope this helps, happy to discuss here. Or if you prefer privately feel free to send me a message.