The FXR's are all rubbermount and vibration is not an issue as long as all the rubber mounts are still good.
The speedo is front wheel driven so any frant wheel driven speedo that works with a 19" wheel should work as long as the front wheel drive is on the correct side.
I have an 83 FXRT Shovelhead and love it. Parts are not that hard to find as most of them were used on many different year bikes. The only thing that will be tricky is the exhaust since it only fits 2 years (82 & 83). The FXR shovels were only made for those 2 years.
The vin checks out good. You can check it yourself here ...
http://www.bigboyzcycles.com/vin.htm
It will be a tinkerer type bike with it being as old as it is.