That's pretty dam good!! And I LOVE those 87 tank decals!!
That 3rd gear slight change is not worth the compromise of the metal lost within the gear hub itself. I have 3 87 motors, all with "I don't know whats wrong with the gearbox??" I love buying those. And why can't every owner realize that the cranks have LH threads. I have about 8 destroyed RH threads that are backwards threads.
Also, I HATE that gearshift plate!! It shifts so positive but it seems as if Honda hardened these just a bit too much. Did one year have shift lever "lightening holes" or was that both??
Both years with that oil drain, thank you Japanese engineer!!
Maybe the helmet holder was just one year; Maybe not, I forget!!
I just glanced at your changes; I'm not sure if you mentioned the clutch disengagement bushing being different. The 87 has a shoulder on it so it sits within a seat to separate the plates when the clutch hand lever separates the clutch plates. EDIT, I see where you said "clutch shifter rod". I guess I didn't understand what "rod" meanted but it's just Cahb Pahts or "carb parts" LOL. These guys all bust my balls.
Oil orifices in some dowel pins are changed to meter the oil flow differently, so wherever they are, the STUFF gets a bit more oil.
The larger diameter large kicker shaft has round holes and thew other year has elongated holes (forget which year is the one people want. But, I have bored a clutch case for the larger shaft and got a stock rubber coated seal sizes at my bearing shop so I didn't have to open that hole too.
The decompression seal is DC'd so my bearing shop gets me rubber coated dual lip seals that are 1mm less in width but the ID and OD are stock; and cheaper at the shop
The clip for that shaft is gozo as well so I just use a regular circlid.
I think I showed a few of those items if you google "3wheelerworld 20 day build"; Or stuff Dirtcrasher in that search, reword it and you can find it.
I took pics mostly of the changes I'm fairly certain of.
I wish Honda left ATC on the seat sides and Honda on the back. I only have 2 backups 
Did both years have the same fork boots number or accordions?? (lack of a better word 
Good ol Honda, always making tiny changes in hopes to improve it!! I love those valve eccentric adjustment changes; Best idea ever!!
Honestly, when I build one, I never use the 87 3rd gear but always the kicker shaft and that seal I can buy. Opening that bore is chicken when you have a mill with an adjustable boring head; he he he he he he he !!!! 83/84 250R 35MM forks help allot as well!!
You covered this awesome (and I think it should be a sticky), great job!!; I think I have just a couple more written down but I have to find my "swap" book to check it out. Extremely good information on your part!! You bagged it very well!! I personally say THANK YOU!!
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country