From what little I've learned so far, the 86-93 are different from the 94-06. All the ones on ebay are the 94-06. I checked...lol
The Speedo is usually off by about 3-4% unless you put a 'winged' size tire on the front (130/70r18 on mine pretty much 'zeros in' the speedo on mine). The 'wing' tires are heavier though, and change the handling characteristics of the bike (won't lean into turns as easily).
So yeah, 70 MPH indicated will usually be about 67-68 MPH actual with 'standard sized' tires.
As for the differences pre-post 93/94, that mainly relates to the front forks/suspension/wheel. Most components didn't change at all between the model years. I'm sure the pre-94 folks can point out the other differences, but I don't think the footpegs changed at all between all model years.
I put 2" handlebar risers on my bike, and this helped my posture considerably. That being said, due to the 'dreaded handlebar buzz', you may want to look at the other handlebar mods (i.e. installing 'classic' handebars, helibars, etc.) if the buzz at the higher RPMs seems to be an issue for you. If your bike isn't 'buzzing the handlebars' too much, though, then no worries.
Finally, yeah I have to pay particular attention to the speedo, as this bike is VERY SMOOTH at higher speeds. If you aren't paying attention, adding 10 mph to your speed while you aren't paying attention is easy to do. Connies have no issues going into the triple digits HP wise, although any weaknesses in your suspension/tire balance setup become noticable in the triple digits. I'm older now, so I'm kind of over the triple digit thrill...
I doubt you will ever hit 150 on this bike though. That is mostly for show... reported top speeds on this forum for the Connie fall in the 130+ MPH range, and I don't remember any reports of 140+ (The guy with the ZZR-1200 engine might be able to go that fast, and I don't know what Shoodaben's top speed is).
One of my favorite things about the Connie is how easily you can increase your speed while doing passing maneuvers, even uphill. Yeah she has power to spare going up hill. Just drop her into 5th and off you go!
